Earlier this year, Sun made many in the world angry and scared when they announced that portions of the MySQL code base would go closed source. After the inevitably stream of flak they received from the community regarding this, they did a very quick about face and said they'd consider rescinding those plans.
Now, just a few weeks later, the MySQL team has made an official announcement that confirms those hopeful rumors. MySQL will not close-source portions of their codebase, keeping the server completely open, including the encryption and compression mechanisms. They are still allowing for 3rd-party, closed-source commercial add-ons, along with the traditional community-driven add-ons. The change in tone comes as a welcome sign and a sigh of relief from many who feared MySQL would die a slow death, choked by Sun trying to squeeze money out of it.