Phew, I'm finally back to work on FreeBSD OIS port. I've tried that SDL patch from tracker, but unfortunately I couldn't make it work. ConsoleApp demo complains that SDL not initialized, and even if I change throwing exception to SDL_Init call, no events will be reported (though mouse freezes until I kill ConsoleApp). Maybe because there's no application window.
But after looking through linux/* stuff more closely I've realized how careless I was - actually linux/input.h is only needed for joysticks, and mouse+keyboard support compiles without any modifications. ConsoleApp also works and is reporting events. I have some ideas (involving libusbhid) on how to make joysticks work, but I'm not sure about feedback support. This will require some more time for experiments, but for now port with mouse and keyboard support is ready.