I did some work on Logitech FFB drivers for Linux and there were no black helicopters circling my roof nor angry emails in my mailbox. Valve has also released their "SteamOS" which is pretty much their own Linux distro, so if there were any patent issues, they'd know. As far as I know you can freely write whatever you please. I'm not a lawyer but as long as you're not making money using someone else's IP - whatever that actually means - the companies can't really get at you. As a game developer you'd be just using some API and I can't imagine how could anyone use that as a basis for a lawsuit. iRacing has recently released Mac and Linux version and they had no particular issues on this front.
That is reassuring. I don't really understand how someone can have a patent on force feedback, it's like having a patent on a "roof" or a "knife" or "walking". Just stupid, so I hope there isn't a problem with it.