Did not know about that blog, thanks.

Veloren, open-source voxel game inspired by Minecraft, Zelda BotW, etc.

Or the Libre Game Wiki.

Thank you for this thread. I know it's really oldschool but if it will be possible to make OP to be 1st of the list for example A-G with links to the rest placed in your other edited posts. Some of them are not so importent for this topic, no offense.

Looks interesting.

Dungeon Master / Chaos Strikes Back for Windows (and Linux, Raspbian, MacOS X, Pocket PC) : http://dmweb.free.fr/?q=node/851

http://sebastianmihai.com/

From what I found in the site, includes multiple open source games for multiple platforms, and even a 16-bit open source OS.

Interesting, I guess, but I didn't see any source code links anywhere.

At the bottom of the "older versions" section, just before "How to run the game".
It's not the latest version, though.

OK, thanks. I guess I'm blind. It's too old to be of any use to me without serious work, though, which I'm not willing to put in at this time. I wonder if the author(s) could be convinced to put up the latest on github or bitbucket, but I'm not going to spend time chasing that, either.

https://zerok.itch.io/zero-k
Leave this as a place holder. I think I will be free in a couple of weeks and will update the hole list :)

BlindJump, for the GBA and PSP.

Github: https://github.com/evanbowman/blind-jump-portable#building

Itchio (links to the Github page): https://evanbowman.itch.io/blindjump

The GBA version comes already compiled and is the downloadable .gba file in the releases page. The PSP version needs to be compiled from source and currently has no audio. License included in the end of the README.md.

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Skyland, for the GBA.

Github: https://github.com/evanbowman/skyland

Itchio: https://evanbowman.itch.io/skyland

License listed here: https://github.com/evanbowman/skyland/blob/master/LICENSE

Fireman - https://lacoste42.itch.io/fireman
Platform: GameBoy Color/GBC
The ROM is the downloadable .gbc file. Also includes the GB Studio source code, but no license is included, so you may want to ask the dev what are the conditions for use.

Project Avenue | Windows
https://insighted.itch.io/project-avenue
https://github.com/InsightGit/Project-Avenue
https://gitlab.com/insightgit/Project-Avenue-Concept

Morpheus | GBA & NDS
https://insighted.itch.io/morpheus
https://gitlab.com/insightgit/Morpheus
https://github.com/insightgit/Morpheus

TouristTycoon | Linux
https://insighted.itch.io/touristtycoon
https://github.com/InsightGit/TouristTycoon2
https://gitlab.com/insightgit/TouristTycoon2

Also a game engine by the same dev: Jetfuel Game Engine Alpha
https://insighted.itch.io/jetfuel-engine
https://github.com/InsightGit/JetfuelGameEngine
https://gitlab.com/insightgit/JetfuelGameEngine

Free Heroes of Might and Magic II (fheroes2) is a recreation of HoMM2 game engine.
This open source multiplatform project, written from scratch, is designed to reproduce the original game with significant improvements in the gameplay, graphics and logic (including support for high-resolution graphics, improved AI, numerous fixes and UI improvements)

Main page:
ihhub.github.io/fheroes2

Github:
github.com/ihhub/fheroes2