Sun has lost the stickiness test. MySQL boss Marten Mickos, the operation’s former CEO and senior VP of Sun’s database group since its acquisition almost exactly one year ago, is following co-founder and MySQL’s original developer Monty Widinius out the door. Sun lost the open source database’s other co-founder David Axmark a few months ago.

Monty’s decision, in the works for months and all wrapped up with his perception that Sun was mishandling MySQL development, was still “pixel-ating,” so to speak, on his blog when news of Marten’s exit broke.

Monty was unhappy with MySQL 5.1 being rushed out the door and with the community’s access to the database’s source code under Sun.

Mickos, like Axmark, apparently felt stifled inside a big company and maybe never intended staying longer. He is quoted as saying in his farewell address to the troops, “I love the challenge of an unproven value proposition and I being the top policymaker, building new things.”

Newly rich entrepreneurs rarely stick around long after acquisition but the departure of these guys has to send the chill of a confidence crisis down the collective spine of the MySQL community and user base. Other MySQL people may also jump ship.

Sun has a lousy track record with its software acquisitions. Heck, Sun has a lousy track record with most acquisitions period and MySQL cost it an over-priced billion dollars. Sun has a habit of overpaying for properties. Some people are born to pay retail.

It has subsequently written off a piece of the purchase price.

Marten’s departure was the signal for Sun to reorg. It’s made VP Karen Tegan Padir, who has survived 16 years off and on with Sun, responsible for a combined MySQL-Software Infrastructure Group that includes the Glassfish application server, identity management, SOA and the Java Enterprise System.

Sun has been depending on open source software to sell its hardware; Sun’s business is in the tank and it hasn’t ever been brilliant at monetizing any of its software but MySQL sales were reportedly up 55% last quarter. It looks like Mickos knew how.

Padir led the technical due diligence on MySQL before the acquisition and its engineering integration afterwards. She joined Sun in 1993 and rejoined again in 2005 after a year at Red Hat as VP of engineering for infrastructure technologies, its aborted desktop software initiatives. She was previously responsible for J2EE at Sun.

She was only saying last week in a conversation about Glassfish that she thought JBoss suffered from its acquisition by Red Hat and subsequent departure of its guiding light Marc Fleury. Hmmm.