Folken has released under the GNU/GPL v3 license his shoot em up game based on the popular manga and anime series Mazinger Z, which can also be bought on an online store as a physical 2 DVDs copy of the game + the sources.
The game can be downloaded from Github (https://github.com/mxfolken/MazingerZ). The iso images must be burned and can be played either on a real console or a PS2 emulator like PCSX2.
To buy the commercial release, simply get it through this Mercado Libre item.
A video of the gameplay can be seen on https://vimeo.com/235471984 and you can discuss this game on the forum post: http://forum.bennugd.org/index.php?topic=4599.0;topicseen