MySQL co-founder David Axmark has quit, saying that he no longer enjoys working for the company since the merger with Sun Microsystems.

Axmark was key to the development of MySQL as an open source product, and is a strong advocate of the free software movement. He will continue to work for Sun on a consultancy basis.

"I have thought about my role at Sun and decided that I am better off in smaller organisations," he wrote in his resignation letter, according to Kaj Arno, head of MySQL community relations.

"I hate all the rules that I need to follow, and I also hate breaking them. It would be far better for me to 'retire' from employment and work with MySQL and Sun on a less formal basis."

The resignation will be a blow to Sun's efforts to integrate MySQL following its billion dollar purchase of the company in January. Another founder, Michael 'Monty' Widenius, is reportedly unhappy at Sun and is also considering leaving.

"I wish David would have stayed longer at Sun, but I understand why he decided to resign and I respect his decision," said Arno.

"I am happy that he's fine with working as a consultant for Sun, doing speaking engagements and connecting us with his huge network. It is very much appreciated."