Hi, I have written a distributed system of applications which run a servo controller for hydraulic systems. This was all done with C++ in windows. It has been decided that we will run some version of "Unix" on the pc which actually controls the electronics and windows on other computers for user interface. The reason is obvious: We need realtime control in an application which interacts with the drivers. My question is what to use for the OS. Linux has a much larger developer base and is probably pretty stable. FreeBSD has rock solid stability, but I don't want to be a victem of any major changes taking place in this OS in the next couple of years.

Any advice?

If you are talking major OS changes in terms of years, they all will. Take a look at the evolution of any OS in a 2 year span.

Anyway, FreeBSD is a solid performer minus the bloat associated with some of the newer versions of say Red Hat. Debian is solid too. I would suggest testing at least three different OS'es and choose the one that is easiest to setup and configure for your needs plus offers the best stability and performance. Choosing one based on someone elses opinion might not give you the best.

I am a big proponent of taking the time up front on a project to do it right. If not you end up having to do it twice.

Good luck with this.