Debian Font Licensing Criteria for Main Archive

Debian maintains strict standards for packages entering its main archive, requiring all software, documentation, and typefaces to adhere strictly to the Debian Free Software Guidelines (DFSG). For fonts to be accepted into this primary repository, they must not only carry a recognized open-source license but must also provide verifiable source files, allow unrestricted commercial and non-commercial redistribution, and permit derivative works without burdensome legal restrictions.

Adherence to the Debian Free Software Guidelines (DFSG)

To enter Debian main, a font license must satisfy all ten criteria of the DFSG. The most critical requirements during license audits include:

  • Unrestricted Redistribution (DFSG 1): The license must permit anyone to sell or give away the font as part of an aggregate software distribution without requiring royalties or fees.
  • No Discrimination Against Fields of Endeavor (DFSG 6): Licenses that prohibit commercial usage, restrict deployment to non-profit entities, or ban specific fields such as government or military use are strictly forbidden. Common freeware clauses like "free for personal use" immediately disqualify a font.
  • Permission for Derived Works (DFSG 3): Users must have the legal right to modify outlines, add glyphs, alter kerning, and redistribute those modified versions under the same terms. Licenses containing "No Derivatives" (ND) clauses fail this requirement.

The "Source Code" Requirement for Fonts

DFSG 2 requires the availability of source code, defined as the preferred form for making modifications. For digital typography, this is one of the most strictly evaluated hurdles:

  • True Source Formats: Debian package maintainers and the FTP master team evaluate whether the distributed files are the author's working format. If a font was created using FontForge (.sfd), Unified Font Object (.ufo), Glyphs (.glyphs), or proprietary tooling, the compiled binary (.ttf or .otf) is treated as executable code. Providing only the binary without the editable source violates DFSG 2.
  • Reproducible Build Toolchains: If a source format exists, Debian requires that the compiled font can be generated from that source using entirely free tools already present in the Debian archive. If compiling the font requires proprietary software, the font cannot be included in main.
  • Direct Binary Exceptions: If the author created or edited the font directly inside a binary container without a separate source file, the binary itself may be accepted as the source, provided upstream explicitly confirms this development practice.

Handling Renaming Clauses and the SIL Open Font License

DFSG 4 permits licenses to require modified versions to carry a different name from the original design to preserve the author’s reputation:

  • Reserved Font Names (RFN): The SIL Open Font License (OFL) is the industry standard for open fonts and includes a mechanism where copyright holders can declare Reserved Font Names. Debian recognizes the OFL 1.1 as DFSG-compliant, provided that any RFN terms are cleanly documented.
  • Clear Renaming Rules: If a font is modified within Debian or by downstream users, the license must allow redistribution under a different name without requiring permission from the original author.

Commonly Accepted vs. Disqualified Font Licenses

Debian strictly validates licenses against established legal precedents maintained by the project:

  • Approved for Debian Main:
    • SIL Open Font License 1.1 (OFL): Accepted with or without Reserved Font Names.
    • GNU General Public License (GPL) with Font Exception: Standard GPL terms with an explicit exception allowing documents embedding the font to remain under their own licensing terms.
    • Permissive Licenses: MIT (Expat), BSD (2-Clause or 3-Clause), and Apache 2.0.
    • Public Domain / CC0: Unconditional dedications to the public domain.
  • Disqualified (Rejected or relegated to non-free):
    • Creative Commons Non-Commercial (CC-BY-NC): Fails DFSG 6.
    • Creative Commons No-Derivatives (CC-BY-ND): Fails DFSG 3.
    • Microsoft Core Fonts (EULA): Redistribution is restricted and modifications are prohibited.
    • GPL without Font Exception: Incompatible with typical font usage due to copyleft contamination of documents that embed the font data.