The LGP Copy Protection (DRM) was added at some point.
Demo available. Requires Linux kernel 2.2.x+, glibc-2.1+, X, 300MHz x86, or PPC CPU, 64MB RAM, 500MB HD, 2x CD-Rom, 4MB video card, OSS Compatible sound card.
The Linux version is not on Steam. It is the Windows version being sold as a Linux game. However, the current development team has access to the source code (documented in Polish). So a real Linux update may yet be offered on Steam.