Julian C Gollop (of UFO: Enemy Unknown and Laser Squad fame) has stated in the Laser Squad Nemesis forums that the Linux client is still in their plans, and will come out this year. In the meantime, the “software engine” version of their client has been reported to work well in Winexand VMWare, so for some people it’s playable in Linux now. BTW, LSN is doing quite well, having recently reached the 3000 subscribers mark. The next patch will probably be coming out this month, bringing along the third and last playable race, the Spawn.
The forum statement mentioned can be found in the Laser Squad Nemesis: OT, linux thread.