SIL OFL 1.1, Clause by Clause: Boundaries and Duties of the Open Font Licence
SIL OFL is the de facto standard for open fonts - Source Han, LXGW WenKai, Smiley Sans and Inter all ship under it. We unpack it as four permissions, two prohibitions and three duties, then explain reserved names, embedding and derivatives in practice.
1. The four permissions
Article one grants four freedoms. Use: any person or company in any context - advertising, publishing, film, software, trademarks - pays nothing and asks no one, forever. Study: font sources (SFD/Glyphs) should be public and analysable. Share: the files may be copied and bundled with software or documents. Modify: reshape glyphs, extend coverage, build derivatives. Crucially, works made with the font carry no infection: your poster, book, app screens and logotype designs are entirely yours - OFL governs only the font file.
2. The two prohibitions
No selling the font files by themselves: bundle them with software or documents, but never package them as the product or drop them into paid asset stores. No Reserved Font Names in derivatives: the names listed at the top of the licence file - Source, Noto, LXGW WenKai, Inter - belong upstream; your modified release must ship under a new name so users cannot be misled by divergent quality. That is why the community names each fork separately.
3. The three duties
Distribute the licence text: every copy of the font travels with OFL.txt. Keep derivatives under OFL - the only copyleft point in the licence, and it touches fonts only, never your app code or artwork. Do not market derivatives under the upstream author's name. Web use (@font-face, Google Fonts embedding) and software bundling count as distribution, so the shipped OFL.txt and NOTICE files are your compliance evidence; outputting rendered images or video carries no duty at all.
4. OFL against the neighbours
Against Apache 2.0 (Roboto): Apache lets derivatives be relicensed, even closed - keep notices, note changes - looser than OFL. Against GPL+Font Exception (WenQuanYi Zen Hei): the font is GPL, but the exception frees embedded documents and proprietary software; raw redistributions still owe source. Against CC0 (Huiwen and friends): public domain, no duties, no reserved names. Against corporate declarations (PuHuiTi, HarmonyOS, MiSans): non-standard text, usually anti-reverse-engineering plus no standalone sale, but with explicit allow-lists. Stability ranking when choosing: OFL > Apache > corporate declaration > individual statement.
5. Action checklist for designers and developers
Design handoff: archive the OFL.txt plus a dated screenshot of the licence page in every project kit; rename any file you reshaped. Front-end: comment the stack with source and licence; when self-hosting woff2, drop the licence text under /fonts or in a LICENSES folder; Google Fonts delivery of Noto or LXGW is self-documenting. Legal ops: maintain a company white-list of approved commercial fonts, run new entries through the five-step check, and re-review declaration-style licences quarterly.
This site is an index of publicly available information. It does not host, mirror or distribute any font file and does not warrant any licence. Rights holders may change terms, split free and paid editions, or withdraw a permission at any time. Before commercial use, verify the licence on the official page and keep a dated screenshot as evidence. For trademarks, overseas publication and large-scale embedding, consult an IP professional.