Developer psxdev has adapted the recent openGL ES PS4 port from flat_z to liborbis and the open source SDK from hito.
In plain English: there is now a way to get hardware accelerated graphics on PS4 homebrews compiled with an open source solution.
I will not hide that it is still unclear to me if there exists a 100% “clean” (as in, not using any “leaked” official tool) way to produce a PS4 homebrew from start to finish: the current method assumes you are loading the homebrew from a PC connected to the PS4, rather than installing a pkg file onto the console.
However, the readme from psxdev is extremely detailed, and frankly this is probably as detailed as it will get in order for people to take this and do something cool with it.
If you have a hacked PS4, a significant chunk of free time, and an interest in creating homebrew apps or games, I urge you to give this a try.