Open Source database vendor MySQL AB released its latest incremental
release last week (version 4.0.20), but according to some in the
community, it still doesn't address what some say serious licensing
concerns. The licensing issue prevents it from being included in some
Linux distributions and working together, from a licensing perspective,
with PHP. Last week, Red Hat's community Fedora Project released Fedora
Core 2 and for all of its updated and improved packages, it had one
notable omission: the 4.x version of MySQL.

http://newsvac.newsforge.com/newsvac/04/05/24/2113235.shtml