URL: http://castle-engine.sourceforge.ne
This URL misses final "t" of course :), it should be http://castle-engine.sourceforge.net/ . The engine description (downloads, documentation, details about license) are on subpage http://castle-engine.sourceforge.net/engine.php .
License: LGPL-2 + extention allowing statically linking to non free software
It may be worth mentioning that this is exactly the same license as used for FPC and Lazarus units (FPC RTL, Lazarus LCL). And FPC and Lazarus are already packaged by Debian :)
Regards, Michalis