I would think that if Windows doesn't support a specific signal, os.kill should raise a ValueError.  But I'm an outsider here, I know nothing about how Windows works for this except what I'm reading here.  

To answer your question: there are many reasons to call kill on unix, and only a few of them kill the process.  Kill is just an historical name, it really means 'send a signal'.

In a broader picture, I think that os.kill calls should have the same "meaning", insofar as possible, on both linux and windows.  Having a single API with the same syntax but different semantics on different platforms sounds bad to me.