Oracle, ZFS, and Linux (and Solaris)
A commentator on my entry on GPL'ing ZFS raised a good issue:
But don't you think it would have been reasonable for Oracle to relicense ZFS upon buying Sun, so they could use it for their own Linux distributions and wouldn't have to reinvent the wheel and support BTRFS development?
In my view, the core issue for Oracle with this is that GPL'ing ZFS gives it to all Linux distributions, not just Oracle's; it's an even greater gift to all Linux distributions if Oracle then also ports ZFS into the Linux kernel. Such a move also does some amount of damage to the remaining attractiveness of (Oracle) Solaris. All of this still might make sense for Oracle to do, but it depends a lot on how Oracle sees both their Linux distribution and Solaris.
I think that Oracle doing this makes the most sense if Oracle sees Solaris as a sideline and expect to be the leading commercial Linux distribution; then any harm to Solaris is unimportant and while ZFS benefits all Linux distributions, Oracle gets the largest benefit. Reversing this gives us the worst case for Oracle, where Solaris is supposed to be as competitive as possible and Oracle Linux isn't a serious player.
I basically have no idea where Oracle is going with Solaris. However, I don't think that Oracle expects Solaris to be big; the time of commercial Unixes has basically passed and Oracle's moves with Solaris don't seem calculated to increase its popularity. There might still be significant money in large enterprises and legacy customers, but even if so I doubt many of them would jump ship to Linux just because it now has ZFS.
I'm sure that Oracle would like Oracle Linux to be the biggest commercial Linux distribution, but at the same time I'm not convinced that that's likely or that Oracle expects to get there any time soon. Also, GPL'ing the ZFS code isn't immediately helpful to Oracle Linux (or any other Linux distribution); it only becomes helpful once ZFS gets integrated into the kernel, and that would probably take years (and have to be funded).
Given all of this, I've wound up thinking that GPL'ing ZFS lacks a clear benefit for Oracle (well, one beyond good PR). Especially, it doesn't solve any problems for Oracle; both ZFS and BTRFS would need a good amount of Oracle's engineering effort before they became ready for production. While it's true that someone else might integrate ZFS into the Linux kernel, saving Oracle the effort, it's equally possible that someone else would do a bunch of work on BTRFS.
(Given that helping create a new filesystem is more interesting than the drudgery of porting a large complex chunk of Solaris kernel code to Linux, it's probably easier for Oracle to recruit good kernel programmers to work on BTRFS than on a hypothetical ZFS Linux port.)