You want to know where the line is ? It's right there in front of your eyes :
Can you improve/fix/increase performance of GLES/GL with what have been released : no
Could you do such things if the firmware was opensource : yes
Then go compare other GPU, for instance firmware of AMD or NVidia GPU are mostly glorified register writter engine that are there so one does not need to constantly use the CPU to change GPU state. You can improve the opensource GPU driver for AMD or NVidia without knowing anything about the firmware. For this broadcom GPU you can't.
Which is why me and many other open source GPU driver developer just see this announcement as a complete lie.