I can understand where patents apply. The only place it should apply is quite simply plagerism. ZFS doesn't plagerize WAFL. However, a patent currently applies to the broader concept. Like anybody can tell a story, anybody can code...how the story is told makes the difference, much like the quality of the code, whoever does it better deserves the sales, not the damn inventor! A patent is unamerican as it attempts to stifle competition.
P.S. If UNIX were under a patent, then any Unix-like system would be violating it since it copies the concept of Unix (i.e. the look, the API, ... everything).