Very interesting.  Not sure what to make of this.  I can't imagine them pouring effort/support into PostgreSQL AND MySQL.  So, my thoughts are either:

• Sun bought MySQL just for the name/installed userbase and intend on porting/rebranding all the good stuff from PostgreSQL into MySQL and actually turn it into an Enterprise database (not just a beginner's first database/dynamic web backend).
• Sun bought MySQL for the technology.  In which case, I do believe they've collectively lost their minds.