Licensing to decide the result of gcc vs llvm?

This section is a little bit misleading.

"One advantage (from Nvidia’s point of view) not mentioned is that llvm is licensed under a BSD style agreement. This means Nvidia don’t have to release the source code of any modifications or additions they make (they said these will be kept closed source); gcc is licensed under the GNU general public license which requires source to be released. Arch rivals AMD (well, the ATI bit of AMD that does graphics hardware) also promote llvm and I’m sure Nvidia does not want to help them in any way."

The GPL does not require the modifications to the source code to be released. It just states that if the modified software is distributed, it must comply with the well-known GPL requirements.