Are you sure? I was reading the box and don't say nothing about Bungie only godgames or something like that and and still appears in Take2Two page
http://www.take2games.com/index.php?...yth3&p=support
EDIT
It seems this answer the question
http://flyingflip.com/index.php/faq
***Q. Is the Myth series open source?
A. No. The Myth III source code is owned by Take Two Interactive Games. The series was obtained by Take Two when Bungie was purchased by Microsoft. As part of the stock-buyout, Take Two received the rights to the source code and the name Myth. Neither FlyingFlip nor any other myth developing group owns all or any part of the Myth source code from any game.***
For what is said there it looks when Bungie was bought by M$ Take2 retained the rights of the Myth series