They are claiming that the FAT filesystem's patent shouldn't have been issued due to Prior Art. For those unfamiliar with the patent process, when you submit a patent, it must be reviewed and the patent office must examine whether there are any other pre-existing things either already publicly available, or patents issued on the idea. Asking for a review could lead to revoking the patent, which at this point is inconsequential to MS really, considering their operating systems run with NTFS or newer filesystems. It will not really affect any users, as far as I can tell.

Groklaw has an article on it: http://www.groklaw.net/article.php?s...40415155729460