Crystal Space

Crystal Space is a multi-platform game engine that runs on many platforms with different graphics libraries (Dirext X, OpenGL, etc.). In case you wonder whether it is listed as a GUI toolkit; it has a windowing system that is multi-platform too.

If you are interested, three versions are available on the intranet here.

features

• Platform independent widgets
• Themes
• OpenGL integration

platforms

• GNU/Linux
• general Unix
• Windows
• Windows NT
• OS/2
• BeOS
• NextStep
• OpenStep
• MacOS/X Server
• DOS
• Macintosh

It can optionally use OpenGL (Windows, GNU/Linux, Mac, OS/2, BeOS), Direct3D (Windows), Glide (GNU/Linux), GGI (GNU/Linux), Allegro (GNU/Linux, DOS), X11 (Unix or GNU/Linux) and SVGALIB (GNU/Linux). It can also optionally use assembler routines (GCC/DJGPP, Visual C++, NASM and Intel only currently) and MMX.

pricing

That's simple, it is free and available under L-GPL (Library/Lesser General Public Licence).