David Axmark, a cofounder and former lead engineer for MySQL, has resigned from Sun Microsystems a few weeks after another cofounder said he may also leave the company.

"I have thought about my role at Sun and decided that I am better off in smaller organisations," Axmark wrote in his resignation letter, according to a blog post Tuesday from 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," Axmark wrote. His last day with Sun will be Nov. 10, Arno said via instant message from Germany.

Axmark filled several important roles at MySQL over the years, including head of engineering, head of internal IT and head of community relations. It's because of Axmark that MySQL is open-source software, according to Arno. Another cofounder, Michael "Monty" Widenius, had planned it to be closed source, he said.

His departure will be a setback for Sun, which acquired MySQL for US$1 billion in January and hopes to attract new developers to the database.

Early last month Arno confirmed that Widenius was also thinking of resigning from Sun. He is still with the company, but his future there is still "hard to predict," Arno said Tuesday.

Axmark is an "important figurehead" at MySQL and someone who recruited many of its top engineers, Arno said. But his role lately has been primarily speaking with the press and liasing with the open-source community, according to Arno. Axmark will continue to do consulting and speaking engagements for Sun, he said.

"Emotionally, it's a sad moment to see a cofounder leave -- but the day-to-day impact is low," Arno said via instant message.

Marten Mickos, MySQL's former CEO, continues to lead the database group within Sun, and Jeffrey Pugh is still head of engineering, Arno said.

Axmark couldn't be reached for comment Tuesday. Arno said the things he disliked about being part of a large company were "mundane things" like having to turn in expense reports, order travel and change his e-mail to "@sun.com."