Marten Mickos, the longtime CEO of MySQL who eventually sold the open source database company to Sun Microsystems for $1 billion, has taken a new job as CEO of Eucalyptus Systems, the company said.

Mickos is staying in the open source world but jumping on a newer computing trend, cloud computing. Eucalyptus makes an open source software platform for building private clouds, or data centres in which workloads can be moved around across different systems to maximise efficiency.

The company's software is used as the cloud platform for the Ubuntu Enterprise Cloud, a software package that includes Ubuntu's open source operating system. It is also designed to work smoothly with Amazon Web Services and other public cloud services.

"Eucalyptus Systems has a brilliant team, highly sophisticated open source technology, and an early lead in a market with a massive global opportunity, all the ingredients for major impact," Mickos was quoted as saying in a statement.

"Private and hybrid cloud computing is the future of corporate IT, and for cloud computing to reach its potential, it will have to be built on open-source software such as Eucalyptus," he said.

Mickos was CEO of MySQL for seven years. He helped grow the company into the most widely used open source database before selling MySQL to Sun in 2008. Sun was later acquired by Oracle, prompting much hand-wringing among MySQL users about whether the open source database will continue to thrive.

Mickos was head of Sun's database group for a year but left in early 2009. At Sun he had a brief public spat with Michael "Monty" Widenius, the original developer of MySQL, who complained that Mickos was pushing out software releases too soon and focusing on speed rather than quality. Mickos later said that "a little bit of debate never hurts. This is part of being an open source company."

He has kept a fairly low profile since leaving Sun, although last year he joined the board of directors at RightScale, which makes a cloud management platform.

Mickos is taking the CEO job at Eucalyptus from Woody Rollins, who has been made chief financial officer. Rollins said Mickos will help transition the company from "startup to sustainable market leader."

Eucalyptus began as a research project at the University of California to develop a platform for large-scale, distributed computing projects.