Still no official news on the rumour that Monty Widenius has left Sun, but Dave Rosenberg confirmed over the weekend that he is leaving MuleSource, the open source ESB vendor he founded in 2006 with Ross Mason, creator of the Mule project.

“After two and a half years I’ve decided to transition out of my operating role at MuleSource and will be devoting my full time efforts to a new company I have been working on,” he wrote on Friday. “I initiated a CEO search in June and we expect to have a new person in place by the end of the year at the latest.

“I started the search because I felt like a more ‘professional’ CEO would be able to take the company to the next level–basically I felt like the opportunity was bigger than me and wanted to grow faster. Now that all the pieces are coming together I feel like I can step out cleanly, setting the stage for continued growth,” he added.

On the recent CAOS podcast we discussed Doug Levin’s departure from Black Duck and noted that it would not be surprising to see a number of open source CEOs shifting seats in the forthcoming months as the vendors they have created look to transition to the next stage.

As well as Levin, EnterpriseDB’s founder Andy Astor recently made way for Ed Boyajian, previously vice president and general manager, North American sales at Red Hat.

The only thing about Rosenberg’s announcement that does seem a little strange is the timing, given that the search for a new CEO has been underway for some time but has yet to be completed.

As for his new job, he notes that “the new company will be in stealth mode for a little while, but if you read my blog consistently you should be able to glean some clues.” He certainly has been writing a lot about online video games.