Tetris clones

[Wart]

It was recently brought to my attention[1] that the bsd-games package 
contains 'tetris-bsd', a curses-based tetris clone.  This was an 
oversight on my part, because if I had paid closer attention during the 
review I would have stripped the name 'tetris' and replaced it with 
something less objectionable.  Now that I know, I'll do that anyway.

But the bug report is claiming that all tetris clones are illegal and 
should be removed, not just the name 'tetris'.  What is the legal status 
of tetris (and other game) clones?  Can we get some "official" word from 
a legal department on what is and isn't allowed?

--Wart
[1]https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=238526