This is the "Castle Game Engine",
webpage http://castle-engine.sourceforge.net/. It's focus is on 3D games
and applications, in particular using VRML/X3D scene format
(although other 3D formats are supported as well).
contains a list of features and useful notes for developers.
The API documentation is available online on
it is also available offline in doc/pasdoc/html/ subdirectory of this archive
(just open doc/pasdoc/html/index.html in your WWW browser).
You can compile the engine and examples by various methods.
For example, you can compile all examples by simple "make examples"
executed in this directory.
If you want to use Lazarus (http://www.lazarus.freepascal.org/),
you'll be interested in installing in Lazarus
packages/castle_base.lpk and packages/castle_components.lpk
(see packages/README.txt for more info).
Then you can compile all the examples by opening their .lpi files
and running them as usual from Lazarus.
In case of any questions, ask on our forum or mailing list,
see http://castle-engine.sourceforge.net/forum.php .
Michalis Kamburelis, aka Kambi.