One of the ironies of open source is that choice lies at its heart, and yet in many respects it is a monoculture. Nearly everything is based on the foundation of GNU/Linux, with alternatives such as FreeBSD representing important but relatively peripheral projects in comparison.
Part of the problem is that GNU/Linux benefits from a kind of first-mover advantage: having colonised the free software operating system niche, it now attracts all the main development ideas, strengthening its position yet further. Significant resources would be needed to jump start a serious competitor – of the kind that Sun, with its increasing commitment to open source, is now putting behind its OpenSolaris project.
Of course, that's only part of the solution: to offer meaningful competition – in the best sense – to GNU/Linux, a complete desktop environment is required. Nexenta provides precisely that, putting OpenSolaris at its heart, and adding by-now familiar elements from GNU/Linux:
Nexenta Operating System is a free and open source operating system combining the OpenSolaris kernel with GNU application userland. Nexenta Operating System runs on Intel/AMD 32/64bit hardware and is distributed as a single installable CD. Upgrades and binary packages not included on the CD can be installed from NexentaOS repository using Advanced Packaging Tool.
The official version 1.0 has just been released, so now might be a good time to take a look at this interesting project.