It is. But there is a bigger market for Mac. That'll happen first.
Synergy2 folks can get all three platforms with one source tree, why can't a commercial company like Stardock do the same?
I'm actually quite disappointed in the development of Multiplicity. It's been literally near 2 years since "soon" was first announced for Linux and OSX. Heck, a year ago you said "the installer is being worked on (for OSX)." A year later and still nothing. It's pretty clear Stardock doesn't care about the other platforms.
http://synergy2.sf.net/ for anybody that wants a true multi-platform solution. It might not be as userfriendly, but it works. I use it with OSX, WinXP and Linux with no major problems.
(there are still a few quirks with the OSX server)