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Licensing

Four sets of terms apply in this repository. The boundary follows the directory tree, so the file you are looking at tells you which set you are under.

Path Terms
rom/ GPL-2.0-or-later (rom/LICENSE)
rom/wad/doom1.wad id Software shareware distribution terms
native/ GPL-3.0-or-later (native/LICENSE)
Everything else Apache-2.0 (LICENSE)

Apache-2.0 covers the emulator and the tooling

spec/, refemu/, sqlcpu/, executor/, driver/, scripts/ and docs/ are an RV32IM machine emulator, the driver that runs both modes, and the tooling around them. They implement an instruction set and a client, not a game. None of them contains DOOM source, and none of them is compiled into the ROM image. The emulator runs the ROM the way any emulator runs a program it did not write.

Two files describe the engine without reproducing it. spec/src/native_state.rs names the fields native mode carries between tics, with their types, which is the interface both sides of a differential write. refemu/probe/layout.tsv holds the offsets of those fields in the ROM's structs, computed by compiling the engine's own headers. Both are facts about the program rather than its expression, and they stay under Apache-2.0.

GPL-2.0-or-later covers rom/

rom/ builds the DOOM binary, so everything in it is part of one program with the upstream engine.

  • rom/vendor/doomgeneric/ is ozkl/doomgeneric at commit dcb7a8dbc7a16ce3dda29382ac9aae9d77d21284, unmodified. It carries id Software's DOOM engine sources. Its files state "either version 2 of the License, or (at your option) any later version", which is where the -or-later comes from.
  • rom/patches/ patches those sources at build time.
  • rom/src/ (crt0, the linker script, libc shims, dg_hooks.c, syscalls.c) is compiled and linked with them.

rom/vendor/README.md records the provenance and the integrity manifest. rom/patches/README.md records every deviation from upstream.

GPL-3.0-or-later covers native/

native/ is a derivative work of the engine, in two ways.

  • native/tables/ holds the engine's own data, copied out of info.c, tables.c, m_random.c, r_draw.c, p_spec.c and p_switch.c under rom/vendor/ by native/src/bin/gen_tables.rs: the state and mobj tables, the sprite names, the weapon table, the sine, tangent and arctangent tables, the random table, the gamma table and the rest.
  • native/src/sql/ and native/sql/ reproduce the engine's simulation and renderer function by function as ClickHouse SQL, quirks included, from p_map.c, p_doors.c, p_plats.c, p_floor.c, r_segs.c, r_plane.c and their neighbours. Each module names the C file it reproduces.

The upstream terms allow any later version of the GPL, and this directory takes that option: it is distributed under version 3 or later. Its terms are in native/LICENSE.

The clickdoom binary

driver/ links native/ into the clickdoom binary, so a built binary is one combined program of Apache-2.0 and GPL-3.0-or-later code. Apache-2.0 is compatible with version 3 of the GPL, and a built clickdoom is distributed under the GPL-3.0's terms as a whole. The driver's own sources stay under Apache-2.0; what changes is the terms a binary carries.

The WAD is under neither

rom/wad/doom1.wad is DOOM Shareware v1.9, sha256 1d7d43be501e67d927e415e0b8f3e29c3bf33075e859721816f652a526cac771. It is game data, not source, so DOOM's GPL release does not cover it. It ships here under id Software's own shareware distribution terms, which have always allowed redistribution of the shareware episode.

Do not add a commercial IWAD (doom.wad, doom2.wad, plutonia.wad, tnt.wad) or any WAD whose distribution terms have not been checked. rom/wad/README.md has the full provenance and the checksums it was verified against.

Contributing

Contributions are accepted under the terms of the directory they land in: GPL-2.0-or-later inside rom/, GPL-3.0-or-later inside native/, Apache-2.0 §5 everywhere else. Inbound is the same as outbound. There is no CLA and nothing to sign.