Fully opensource games:
OpenTyrian (engine is GPL, data files are free for non-commercial use)
Ur-Quan Masters (GPL)
UFO: Alien Invasion (GPL)
MilkyTracker (GPL, not exactly a game)
GrafX2 (GPL, also not a game)
Alien Blaster (GPL)
TeeWorlds (Zlib-like license, it’s broken, but old release worked)
Pachi el marciano (GPL).
Games with opensource engine, and proprietary data files:
Free Heroes 2 (GPL, free demo available. My most downloaded app. Also there’s no reason to buy full game, because campaign mode is yet not supported)
GemRB (GPL, Baldur’s Gate engine, free demo available, the only app rated 4.5 stars on Market)
VCMI (GPL, Heroes 3 engine, no free demo, and it’s buggy like hell)
PrefClub (a free Dos game wrapped in a Dosbox)
Commander Genius (GPL, free demo available)
All free demos can be downloaded right from the game.
Also, not my projects, but open source and worth mentioning: http://androiddosbox.appspot.com/ – GPL, Dos emulator, the project is in dire need of a maintainer. You can also compile Dosbox with my SDL port, and it will have some features that are not present in aDosbox, but aDosbox is still better. Also there are lot of commercial Dosbox builds on Market, with different features. http://www.scummvm.org/ – GPL, engine to run old but glorious point-and-click games, they have their own Android build. Several free games are available for download. It can also be compiled with my SDL port, and you’ll have some minor enhancements (like configurable mouse emulation). http://anddev.at.ua/ – contains builds of several console emulators (Atari, Amiga, C64), and ScummVM compiled with SDL, for people dissatisfied with the official build.
My reading of this is that, the sources for many apps are already in project/jni/application/ , a symlink created for the one you want and an interactive script is run, which asks you (on the first go?) do you have a small medium or large screen and whether you want admob: though in the case of Pachi there are about 30 questions. The repo sources are about 200MB which includes loads of games and the README in the root directory explains it clearly:
export NDKBUILDPATH="/path/to ndk"
ln -s ballfield project/jni/application/src
./ChangeAppSettings.sh -a // the interactive script
android update project -p project -t android-15
cd project ;ant debug
which builds Ballfield by default which is just a demo.
So, once the script is fixed to allow automation, we would have to find a way to avoid downloading 200MB repo for each app. There are steps being taken in this regard already for the eyes-free project.