As well as moving away from a completely open model, Sun’s MySQL has bigger issues:

Sun has announced the official release of MySQL 5.1, a new version of the popular open source database software. Although Sun has declared that this version is ready for widespread adoption in production environments, MySQL creator Michael Widenius says that it has “fatal bugs” that seriously undermine the quality of the release.

MySQL creator: version 5.1 released with “fatal bugs”