Fourth paragraph of the story:

Bridgman followed up later with "The main reason for basing this driver on the open source stack was that we wanted to be able to release the new driver in source code form. Given that constraint, leveraging the existing open source code (rather than trying to sanitize a bazillion lines of Catalyst code) was kind of a no-brainer." In fact, he mentioned the open-source WEC7 driver requirement a few times. "We just added two more open source developers (going from 2 to 4) contributing to the upstream code, and I already said that we used the open source driver as a basis for the WEC7 driver because we wanted to release source code for that driver as well."
Get that? :

We just added two more open source developers (going from 2 to 4)
Whohoo! Hey thanks, AMD!