The source is only released from the last build not the current.
U have 2 wait 4 the Final Release, 2 get the source of 0.99
(and probably the source of 1.0? Who knows?)
And olivieryuyu had done a good comment, because mupen is a project by Hac and he's a great coder and if I'm remmber right, than he did this all alone! Try this.