SIL Open Font License

The SIL Open Font License (OFL) is a free and open source software license specifically designed for fonts and related software, enabling users to freely use, study, modify, and redistribute such works while protecting the moral rights of font authors.^[1] Developed by SIL International, a nonprofit organization focused on language technology and linguistics, the OFL was first released in 2005 as a draft and reached its current version, 1.1, on February 26, 2007, with no substantive changes since then but ongoing FAQ updates, the latest being version 1.1-update7 in November 2023.^[2]^[3] The license grants broad permissions for embedding fonts in documents, bundling them with software or hardware, using them in web pages, and incorporating them into designs such as logos or printed materials, without requiring attribution in most cases.^[3]^[4] Key requirements include retaining the original copyright notice, license text, and any associated FONTLOG (a changelog for fonts) in distributions; for modifications, creators must rename the font to avoid using any declared Reserved Font Names (RFNs) and clearly indicate changes, ensuring modified versions remain under the OFL.^[3]^[4] Notable restrictions prohibit selling fonts on a standalone basis, relicensing under incompatible terms, or removing protections for the original author's rights, making the OFL compatible with many other open licenses like the GNU General Public License for combined works.^[3] Widely adopted in the open font community, the OFL has facilitated projects like Google Fonts and numerous libre font families, promoting accessibility and innovation in typography for global writing systems.^[5]

Development and History

Origins and Creation

SIL International, a global faith-based nonprofit organization founded in 1934 by William Cameron Townsend, has long focused on linguistic research, language documentation, Bible translation, and the development of writing systems for underserved communities worldwide.^[6] With expertise in typography through its Writing Systems Technology team, SIL has created comprehensive fonts supporting diverse scripts such as Latin, Cyrillic, and Greek to aid language preservation and literacy.^[5] This background positioned SIL to address emerging needs in open font licensing during the early 2000s, as digital typography intersected with free and open-source software movements.^[2] The creation of the SIL Open Font License (OFL) stemmed from research conducted by SIL staff members Victor Gaultney and Nicolas Spalinger between 2001 and 2004, partly in collaboration with UNESCO’s Initiative B@bel, which highlighted deficiencies in existing open-source licenses like the GPL and MIT for font distribution.^[2] General software licenses often failed to adequately protect font creators' reputations and copyrights while permitting the broad modifications and sharing essential for font development, particularly for lesser-known languages; the OFL was designed to fill this gap by encouraging collaborative improvements without allowing standalone commercial sales of unmodified fonts.^[7] This motivation aligned with SIL's mission to foster an "open stack" for writing systems, enabling fonts to be freely used, studied, modified, and redistributed in support of global language communities.^[3] Early drafts of the OFL were developed in 2004 and 2005, incorporating feedback from legal experts, font designers, and free software advocates to ensure simplicity and reusability.^[2] Community consultations intensified in 2005, including presentations and discussions at the World Summit on the Information Society (WSIS) in Tunis and the Association Typographique Internationale (ATypI) conference in Helsinki, where typographers and developers provided input on balancing openness with creator protections.^[2] The first public review draft (version 1.0-review1) was released in September 2005, followed by review2 in November, leading to the official launch of OFL version 1.0 on November 22, 2005, alongside its inaugural FAQ document.^[2] This release marked the culmination of initial development efforts, with ongoing public reviews from 2005 to 2007 engaging broader typographic, developer, and open-source communities to refine the license.^[2]

Versions and Updates

The SIL Open Font License (OFL) version 1.0 was initially released in late 2005, but the license underwent a community-driven revision process leading to version 1.1. A draft of version 1.1 was submitted for public review in March 2006, incorporating feedback from font designers and open source advocates to refine naming and distribution mechanisms. The official release of OFL version 1.1 occurred on February 26, 2007, accompanied by OFL-FAQ version 1.1, marking the current stable version of the license text.^[2] Key differences between versions 1.0 and 1.1 focused on clarifications rather than overhauling core permissions, which remained permissive for font use, modification, and redistribution. Version 1.1 introduced an optional Reserved Font Names (RFN) mechanism, allowing font authors to explicitly list protected names in the license to control how derivatives are named, preventing automatic reservation of all names as in version 1.0. Additional refinements addressed bundling fonts with software and embedding in documents, ensuring these practices align with open source principles without imposing new restrictions.^[2]^[3] The OFL-FAQ has seen incremental updates to address technological advancements and common queries, while the core license text has remained unchanged since 2007. Notable revisions include version 1.1-update2 in August 2010, which added guidance on Web Open Font Format (WOFF) support for web embedding. In September 2013, update3 incorporated clarifications on webfont usage and integration with platforms like Google Fonts, building on a May 2013 draft that expanded on RFNs. Further updates occurred in April 2019 (version 1.1-update5), December 2020 (version 1.1-update6), and November 2023 (version 1.1-update7), with the latter tackling modern web technologies, variable fonts, and contribution-related questions from the community.^[2]^[3] In November 2023, the OFL project launched a dedicated website at openfontlicense.org to improve accessibility and organization, with automatic redirects from the previous domain scripts.sil.org/OFL. This update did not alter the license text but enhanced resources like the FAQ and historical documentation. SIL International has emphasized the license's stability, stating no further versions are planned, with ongoing efforts limited to maintaining the FAQ to accommodate evolving font technologies such as variable fonts and web standards.^[2]^[1]

License Provisions

Permissions Granted

The SIL Open Font License (OFL) grants users broad permissions to utilize licensed fonts in diverse applications without requiring attribution, royalties, or additional permissions. Individuals and organizations may install and apply the fonts freely in both personal and commercial projects, including books, websites, mobile applications, logos, merchandise such as t-shirts and posters, and other design work. This freedom extends to any kind of output where the fonts are rendered, ensuring accessibility for creative and professional endeavors.^[3] Users are permitted to modify the font software extensively, including editing individual glyphs, adding support for additional languages or scripts, or creating derivative versions tailored to specific needs. Such modifications allow for customization while preserving the open nature of the license, and it is recommended to clearly document any redistributed changes to inform subsequent users of alterations made.^[4] Redistribution of both original and modified fonts is explicitly allowed under the OFL, with derivatives required to be released on the same license terms to maintain the open ecosystem. Fonts may be bundled with software products, such as in PDF documents or applications, or integrated into services like font design tools, facilitating widespread sharing and collaboration without standalone sales of the fonts themselves.^[4] Embedding the fonts in documents, software, or web formats is fully supported, enabling inclusion in static files like PDFs or dynamic web uses via formats such as WOFF and WOFF2, without imposing the OFL terms on the embedding document or application. This permission ensures that the fonts can be securely incorporated while preventing easy extraction for unauthorized redistribution.^[3] The license encourages contributions to font projects by allowing users to submit improvements or modifications back to the original authors, who retain copyright but may choose to incorporate these enhancements into future releases. This mechanism fosters ongoing development and community involvement in refining the fonts.^[3]

Restrictions and Requirements

The SIL Open Font License (OFL) imposes specific restrictions to prevent the standalone commercialization of fonts while allowing integration into broader products, ensuring that the font software cannot be sold independently but may be bundled with hardware, software, or services such as word processors or custom design packages.^[3] This prohibition aims to maintain the license's collaborative ethos, as explicitly stated in the preamble: "prohibiting standalone sales of Font Software."^[8] A key mechanism for protecting font identity is the optional Reserved Font Names (RFN) clause, introduced in version 1.1, which allows copyright holders to specify names (e.g., "Gentium") that cannot be used for modified versions without explicit permission, thereby requiring derivative works to adopt new names to avoid market confusion.^[3] The OFL text clarifies: "You may not use the reserved font name(s) in any Modified Version without permission from the Copyright Holder(s)."^[8] This provision is optional and declared in the copyright statement, enabling authors to safeguard their branding while permitting modifications. The license enforces a share-alike requirement, mandating that all derivatives of the font software remain licensed under the OFL, prohibiting relicensing to proprietary terms or other open licenses that might dilute the original freedoms.^[3] As outlined in the conditions: "No Modified Version of the Font Software may use the Reserved Font Name(s) unless explicit written permission is granted by the Copyright Holder to do so," and all distributions must preserve the OFL terms.^[8] This ensures ongoing openness, with the FAQ affirming: "If you distribute that font to others it must be under the OFL."^[3] Redistributors face documentation obligations to maintain transparency and attribution, requiring inclusion of the full OFL text and all copyright notices in every copy of the font software; documenting modifications (e.g., via a FONTLOG) is strongly recommended.^[3] The license specifies: "Each copy or substantial portion of the Font Software must contain a copy of the above copyright notice and this license."^[8] The FAQ elaborates: "At a minimum you must include the copyright statement, the license notice and the license text."^[3] Finally, the OFL includes a comprehensive disclaimer of warranty and liability, providing the font software "as is" without any guarantees of merchantability, fitness for a particular purpose, or non-infringement, with users assuming all risks associated with modifications or use.^[8] This standard open-source clause states: "In no event shall the Copyright Holder be liable for any claim... arising from the use or distribution of the Font Software."^[8]

Adoption and Impact

Notable Fonts and Projects

The SIL Open Font License (OFL) enabled early adoptions within linguistic and open-source communities, demonstrating its utility for specialized typography. In January 2006, SIL International began releasing its font library under the OFL, including projects tailored for multilingual support in linguistics and minority languages.^[2] A key example is Gentium, SIL's serif typeface launched in 2006, which supports Latin, Greek, and Cyrillic scripts with extensive diacritical marks for accurate representation of diverse ethnic languages.^[9] Gentium, the first font ever released under the OFL, was accepted into the Debian GNU/Linux distribution, highlighting the license's compatibility with free software ecosystems.^[2] The OFL's permissive terms facilitated widespread integration into digital platforms, notably through Google Fonts. Launched in May 2013, Google Fonts initially included several OFL-licensed families, providing web developers with free, high-quality typography options.^[2] As of 2025, the catalog includes over 1,800 font families, the majority under the OFL, enabling billions of web pages worldwide to utilize open typography without licensing barriers.^[2]^[10] One of the most ambitious OFL-adopted projects is Google's Noto font family, re-licensed under the OFL in September 2015 to promote universal Unicode coverage. Noto encompasses over 800 languages and more than 150 writing systems, ensuring consistent rendering of text from any script and reducing "tofu" (missing glyph) issues in global applications.^[2] Several other fonts underscore the OFL's role in user interface, education, and accessibility design. Cantarell, a humanist sans-serif released in 2009, became the default UI font for the GNOME desktop environment, optimizing readability on screens across Linux distributions.^[2] SIL's Andika, a legibility-focused sans-serif, supports Latin, Cyrillic, and Greek scripts for educational materials and literacy programs, aiding beginning readers in thousands of languages using those scripts.^[11] In the 2020s, accessibility-driven fonts like Archivo—a versatile grotesque sans-serif for headlines and body text—and Atkinson Hyperlegible, engineered for low-vision users with distinct letterforms, further illustrate the license's support for inclusive typography.^[12]^[13] The OFL has spurred broad adoption, with thousands of fonts released by independent designers, type foundries, and corporations, encouraging collaborative modifications and derivatives. These resources are prominently featured in open repositories like Fontshare, which curates OFL fonts for commercial and personal use, and Wikimedia Commons, hosting specimens and files for public domain integration.^[14]^[15]^[16]

Recognition and Comparisons

The SIL Open Font License (OFL) received formal endorsement from the Free Software Foundation (FSF) as a free software license on January 23, 2006, affirming its alignment with principles of software freedom specifically tailored for fonts.^[2]^[17] Subsequently, the Open Source Initiative (OSI) certified the OFL version 1.1 as compliant with the Open Source Definition on April 1, 2009, listing it among approved open source licenses and highlighting its suitability for font distribution.^[2]^[18] Community engagement further solidified the OFL's recognition through initiatives like the "Go for OFL" campaign, launched in August 2006 with support from organizations including the FSF, OSI, GNOME, KDE, and the Linux Foundation to promote it as the preferred license for free/libre open source fonts.^[2] Early presentations, such as a lightning talk at the inaugural Libre Graphics Meeting in March 2006 in Lyon, France, facilitated key discussions among developers and designers.^[2] In more recent years, the OFL featured in a virtual Q&A session at the Association Typographique Internationale (ATypI) conference in October 2020, moderated by Dave Crossland, which explored its role in open font collaboration.^[2]^[19] Additionally, a poster on open fonts under the OFL was presented at UNESCO's LT4all initiative poster session in October 2020, emphasizing its contributions to language technology accessibility.^[2] In comparisons to other licenses, the OFL's copyleft provisions and prohibition on standalone sales distinguish it from permissive licenses like the MIT or Apache, which permit such commercial distribution without requiring derivatives to remain open, thereby better safeguarding font ecosystems from proprietary fragmentation.^[3] Unlike the GNU General Public License (GPL), the OFL is more narrowly tailored to fonts, avoiding the GPL's broader "viral" effects that could impose source code disclosure on unrelated software.^[3] It shares similarities with Creative Commons licenses in promoting sharing but is specifically adapted for typography, addressing unique aspects like embedding and naming without the generality of content-focused terms.^[3] The OFL's advantages lie in its balance of openness and creator control, particularly through Reserved Font Names (RFNs), which allow original authors to retain naming rights for unmodified distributions while enabling modifications under the same license.^[3] This framework has earned widespread recommendations from the FSF and OSI for libre fonts, fostering collaboration without fully relinquishing attribution.^[17]^[18] Evolutions in the OFL have addressed practical concerns, such as web embedding, with clarifications in the 2010 FAQ update (version 1.1-update2) confirming that techniques like @font-face or WOFF conversion are permitted as long as the font remains under the OFL and is not extracted for separate redistribution.^[2]^[3] While the license has faced no major controversies, occasional debates have arisen regarding the rigidity of RFNs, with some designers viewing them as overly restrictive for naming derivatives, though many opt out of declaring them to prioritize flexibility.^[20]