All versions of MySQL since 3.23.19 have been released under the GPL, but AFAIK the documentation has always retained its copyright under the ownership of MySQL

All versions of MySQL since 3.23.19 have been released under the GPL, but AFAIK the documentation has always retained its copyright under the ownership of MySQL AB, Sun and now Oracle. At no point was it ever distributed under the Creative Commons or some other free-ish documentation license. When I refer to "the documentation" I'm mostly talking about the web docs at dev.mysql.com, which are are far more important than the man pages. If the man pages are covered by the GPL'd may be a thorny issue. The GPL is not generally applied to documentation.