OPL2 is an open source, extremely moddable replacement for the Polygon Love 2 game engine, written in Python and C++ and using the Panda3D game engine ( www.panda3d.org )
OPL2 is just an engine, you will need the files from the original game to be able to play. OPL2 doesn't contain any copyrighted material from the original game/engine.
While Polygon Love 2 is an erotic/life simulation game, the OPL2 engine does not contain any explicit material itself. OPL2 is heavily moddable and can be used for many other things such as cosplay simulation.
Hongfire thread to talk about the game: http://www.hongfire.com/forum/showthread.php/410086-OPL2-open-source-and-moddable-3d-hentai-game/page27?highlight=opl2
(WARNING! EXPLICIT CONTENT!)
- completely moddable
- viewers/converters and modding tools for 3d modellers for the game's file formats
- 99% of code written in Python and well documented
- wiki and offline PDF docs for everything needed to know about the game/engine
- multiplatform: sourcecode can run on Windows, Mac and Linux, etc.
Opl2 works good.