As far as I know it's still true. Even if you're using those open source graphics drivers you still need the binary GPU blob in order to actually boot the Pi. The Pi's initial bootloader has to run on the VPU and those open source drivers don't - indeed, they're from a related chip that doesn't even have a VPU. Last time I looked there was no documentation for the VPU, no open-source version of the bootloader code, no compiler that targets the VPU, and the only assembler was based on unofficial reverse engineering.

This article makes no promises. It merely states the possibility of having some functionality. Can you find somewhere that provides a fully OSS build for Raspberry Pi?