Kevin, I don't believe that is the case in this instance.  No one is talking about mixing code.  If you do have something however specifically regarding the FSF stance on

ZFS, I'd like to read it - I've searched and haven't been able to find anything.  As I previously mentioned, one would think if the FSF had issue with it they would 

come out and rebuke all the statements out there that say it isn't an issue; especially since Canonical is actively working on it.