We will only support Windows and Mac to start with. We use a different framework then OOTP which is cross-platform as well but I have no access at all to a Linux machine (afaik the OOTP Linux support is done by Paul who has nothing to do with FHM).
For minimum requirements, we have not defined them but if you can run OOTP you should be able to run FHM as well. My two main development PC's (desktop and notebook) are no monsters but run the game pretty well.
