You can use the windows dedicated server EXE together with a recent version of wine (
www.winehq.org).
I did that once and tried it together with SF. The only problems you will encounter are :
- you have to install IE6 (no joke). Steam uses the Windows crypto-API which gets installed by the IE-installer. But to get the installer to work is quite problematic, the best way is to keep wine in 'win98'-mode (if you know wine, you know what i mean

). Of course, if wine can access a windows installation you may be able to skip this step.
- you will need to have an X server or VNC running, because the windows ded server, although being an console-app, won't run with wineconsole.
- because you have an X/VNC server running AND have wine doing its job, your server will need some extra horsepower. My duron 800 was quite overloaded with 6 ppl...
GL