NetBSD 5.0.2 CD, 1 disc set.

NetBSD is a free, secure, and highly portable UNIX-like Open Source operating system available for many platforms, from 64-bit AlphaServers and desktop systems to handheld and embedded devices. Its clean design and advanced features make it excellent in both production and research environments, and it is user-supported with complete source. Many applications are easily available through The NetBSD Packages Collection.

Link: http://www.netbsd.org