Open Source Licenses — Reference Links & One-Line Notes

Permissive

• MIT License — Ultra-simple: notice and disclaimer only.
• BSD-2-Clause — MIT-like; no advertising clause.
• BSD-3-Clause — Adds a “no-endorsement” clause.
• 0BSD — PD-like; even attribution not required.
• ISC License — Modernized MIT; very short text.
• Apache License 2.0 — Patent grant + retaliation; business-friendly.
• Boost Software License 1.0 — Very permissive; popular for header-only libs.
• The Unlicense — Public-domain dedication; sometimes avoided in enterprises.
• zlib License — Minimal terms incl. no misrepresentation.
• libpng License — zlib-style; bans false origin claims.
• NCSA/University of Illinois — MIT/BSD-like university license.
• PostgreSQL License — MIT/BSD-equivalent; easy for commercial reuse.
• OpenSSL (3.0+) — Since 3.0, Apache-2.0; older were dual-licensed.
• ICU License — MIT/BSD-like permissive terms.
• HPND — Historical BSD-style permissive license.
• NTP License — BSD-like terms from the NTP project.
• MirOS Licence — ISC-style with EU-law phrasing.
• PHP License 3.01 — Permissive with “PHP” name-use restrictions.
• PSF License 2.0 (Python) — Essentially MIT-like; used by Python core.
• UPL 1.0 — Short, Apache-inspired, internationalized.

Weak Copyleft

• MPL 2.0 — File-level copyleft with patent grant.
• EPL 2.0 — Module-level copyleft; enterprise-friendly.
• LGPL 2.1 — For libraries; linking OK, modified parts disclosed.
• LGPL 3.0 — v3-based; adds patent and anti-Tivoization terms.
• CDDL 1.0 — MPL-derived weak copyleft (Solaris heritage).
• CPL 1.0 — IBM-origin; predecessor to EPL.
• MS-RL — Reciprocal; requires publishing your changes.
• APSL 2.0 — Apple’s weak copyleft with notice obligations.
• CeCILL-C — LGPL-like under French law.

Strong Copyleft

• GPL 2.0 — Classic strong copyleft; no explicit patent grant.
• GPL 3.0 — Adds patent provisions and anti-Tivoization.
• AGPL 3.0 — Extends copyleft to network/SaaS use.
• EUPL 1.2 — EU license with cross-license compatibility.
• OSL 3.0 — Strong reciprocity incl. network distribution.
• RPL 1.5 — Broad “deployment” triggers sharing duties.
• CeCILL 2.1 — GPL-compatible strong copyleft (French law).
• Sleepycat License — Distribution requires releasing source of the whole work.

Exceptions / Dual / Special

• Artistic 2.0 — Modern Perl license; flexible re-licensing.
• Artistic 1.0 — Older, somewhat ambiguous wording.
• Perl (dual) — Choose Artistic (usually 2.0) or GPL.
• CNRI Python License — Old Python license; superseded by PSF.
• GPL-2.0 + Classpath Exception — Eases linking with proprietary code.
• GCC Runtime Library Exception — Allows linking to GCC runtimes.
• Bison Exception — Generated parsers may use any license.
• LLVM Exception — Apache-2.0 with additional runtime exceptions.

Non-Software (Docs / Fonts / Data)

• GFDL 1.3 — Copyleft for manuals; beware invariant sections.
• CC BY 4.0 — Attribution only; modification & commercial OK.
• CC BY-SA 4.0 — Attribution + share-alike.
• CC0 1.0 — Public-domain dedication with fallback.
• SIL Open Font License 1.1 — For fonts; rename derivatives.
• ODbL 1.0 — Share-alike license for databases.
• ODC-By 1.0 — Attribution for data/databases.
• PDDL 1.0 — Public-domain dedication for data.

Hardware

• CERN OHL v2 — P (Permissive), W (Weakly-reciprocal), S (Strongly-reciprocal) — Hardware design licensing in three variants.
• Solderpad Hardware License 2.1 — Apache-2.0 adapted for hardware.
• TAPR OHL 1.0 — Early copyleft for open hardware.

Use with Caution (often non-compliant / unclear)

• WTFPL v2 — PD-like with profane wording; often avoided.
• Beerware — Joke license; legal clarity is weak.
• JSON License — “Do No Evil” clause; not OSI-approved.

Notes summarize typical interpretations; always read the full text and seek legal advice when needed.