Comment 16 for bug 49052

@laelfrog: this bug is not Ubuntu-specific at all; the author of the code (Roman ZIppel) probably wrote that warning because he was not sure that the code is safe when writing on a journaled partition. The problem is writing on the journal - you can disable journaling on the FS, which decreases the resilience to crashes. According to [1], it can be done from Mac OS X with this command (which I didn't try):
diskutil disableJournal /Volumes/TheVolumeName

it is unlikely that Ubuntu works on this - in the very best and unlikely case, they could sponsor some external developer to fix it. The author of the code is Roman Zippel, and git log fs/hfsplus shows that he has not worked on it actively at least since 9 Apr 2008 [2]. And the driver does not support filesystems bigger than 2TB because nobody has a week (at most) to spend on changing the type used for sector numbers :-( (see git history of fs/hfsplus, on git.kernel.org).

[1] http://www.fsarchiver.org/forums/viewtopic.php?f=22&t=1012
[2] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=76b0c26af2736b7e5b87e6ed7ab63901483d5736