Ok, this might be a completely moronic and stupid question, but I'll ask anyway

I see that more and more people use FPGA-stuff to revive old platforms. Are the cards somewhat compatible, or will complete rewrites be needed?
The thing I'm wondering in particular, is if we can use the Replay Board to run C64-stuff, since that seems to be relatively complete right now
http://www.syntiac.com/chameleon.htmlSo, will I need to buy the Chameleon to do C64-stuff, or will the Replay Board support the same cores? (most likely, there will have to be a few changes, but that should be feasible I hope)