Document the licensing split (MPL 2.0 compiler / Zlib RTL)

• Type: doc (Track D — user/website licensing docs)
• Status: done
• Owner: —
• Opened: 2026-07-04 (surfaced while adding lib/rtl/types.pas)

What

The repo has a deliberate two-license split that is not called out in the user-facing docs:

• Project root LICENSE / LICENSE.md = MPL 2.0 — the compiler (compiler/**) and project as a whole.
• lib/rtl/** (and the wider runtime) = Zlib — every RTL source carries { SPDX-License-Identifier: Zlib } (70/70 files). A permissive choice so the runtime you link into your program is liberally reusable, mirroring how FPC licenses its RTL separately (LGPL-with-static-exception there; Zlib here).

New RTL files should keep the Zlib SPDX header to stay consistent.

Why a ticket

A user shipping a binary needs to know the RTL that ends up in their executable is Zlib (very permissive), distinct from the MPL-2.0 compiler. Today they'd have to grep SPDX headers to discover it.

Do

Add a short "Licensing" section to the user docs (docs/**): state the split, what each covers, and the practical takeaway ("code you compile links only the Zlib RTL; the MPL-2.0 terms apply to the compiler, not your program's output"). Prose only — no code/license-file changes here (any actual license change is a separate decision, not this ticket).

Log

• 2026-07-15 — resolved, commit a880142a.