Scott Long (who together with Ruslan Ermilov were responsible for the 2.2.9
'release') wrote on the freebsd-current@ mailinglist:

The ISO image is valid, but we didn't do things like bump the version
numbers, tag CVS, or build ports. I hand-edited the .TXT files
available from FTP, but the same files in the ISO are the stock 2.2.8
ones. However, the release was built from the RELENG_2_2 tree, so it
actually does incorporate the small handful of changes that went in
after the 2.2.8 tag was laid down. It was a fun little trip in the
Way-Back machine, and the announcement email was meant to poke some fun
at that.


So, even though the 2.2.9 release is mostly an April Fool's joke, it should
actually be fully usable for those few people that still have reason to use
FreeBSD 2.2.x