source?

tbassetto · on April 3, 2014

Got the info by email from a trusted source (I have been a Mozilla contributor)

richardjs · on April 4, 2014

It's also mentioned on his blog, or at least the statement "I’ve resigned as CEO and I’m leaving Mozilla to take a rest..." [1]. Doesn't explicitly say he's never coming back, but certainly says he's leaving Mozilla for a time.

[1] https://brendaneich.com/2014/04/the-next-mission/