Windows-Compatible ReactOS Is Getting ReiserFS Support
While ReiserFS isn't too popular these days and we're not even talking about the more-modern Reiser4 file-system, it seems at least some are interested in supporting the file-system atop ReiserFS. As of yesterday, the ReiserFS Windows driver was added to the source tree but has yet to be enabled.
Already supported on ReactOS other non-Windows-native file-systems like Btrfs and EXT2 while NTFS is obviously most common for these users. You can see my recent test drive of ReactOS over here of the recent ReactOS 0.4.