Widenius and Sun had a slightly rocky relationship since the vendor bought MySQL last year for $1 billion. In a much-discussed November blog post, he trashed Sun's decision to give MySQL 5.1 a "generally available" designation, saying it was riddled with serious bugs.
In a December interview with IDG News Service, Marten Mickos, senior vice president of Sun's database group, downplayed Widenius' criticisms, saying that at an open-source-oriented company like Sun, "people are free to blog about what they want."
And now in his latest blog post, Widenius revealed what was happening in the months prior to his departure, and what he plans to do now.
Rumors that Widenius would resign were circulating around August and September last year, he wrote.
Widenius acknowledged that he told Sun management he would submit his resignation "immediately" because he "strongly believed that the 5.1 release was not ready and that those problems needed to be fixed before it went GA."
Widenius ultimately agreed to stay for three more months "to help Sun work out things in MySQL Development and also give Sun a chance to create an optimal role for me within Sun."
That ended up lasting a few more months, and "the changes I had hoped Sun would apply to in the MySQL Database group to fix our development and community problems did not happen fast enough," he wrote.
In particular, Widenius wanted "the server development to be moved to a true open development environment that would encourage outside participation," he wrote.
He and Sun parted on good terms, Widenius added. "I still think that Sun was the best possible buyer for MySQL and I feel sad that things didn't work out together."
Meanwhile, Monty Program Ab will be "a true open-source company," with only a small number of employees who "strive to have fun together and share the profit we create."
The company will work on the Maria project, a storage engine Widenius and others developed, he wrote.
A Sun spokeswoman did not immediately respond to a request for comment Thursday. Widenius could not immediately be reached for additional comment.