It's not that simple. Intel is not a perfect free software supporter either.
Neither is AMD. NVIDIA is probably the entity that is clearly the most
hostile at the moment.
NVIDIA: We won't support free software in any way.
AMD: We will support free software where it benefits us.
Intel: We wills support free software where it benefits.
AMD supports the coreboot project which is developing a free software
replacement BIOS. AMD has a higher end graphics chipset and would not want to
reveal "secrets" to Intel and/or possible for reasons of digital restrictions
management. I hear this isn't quite the truth although what it points to
(regardless of the exact reason) is that it is believed to be a business
advantage to keep code secret.
Intel: Intel doesn't have anything to reveal. Its only going to benefit by
the release of code for its graphics chipsets. In fact doing so is in Intel's
business interests because it means more developers can optimize code for its
lower performance chipsets. It might be catching up although it still doesn't
have any secrets to reveal that its main competitors don't already know.