Hi Dubfx,
the grs-sgminer is open source. In fact you can compile it directly from github. Its a fork of the original sgminer. Srcxxx is a directx and OpenGL expert. He has managed to improve the groestl and myriad-groestl (actually also others like x11, x13 and x15) kernels. There are others (will not mention their names) that have improved it also. All of them are keeping the kernels internally in order to get profit for themselves.
Srcxxx could also keep it for himself but decided to share his improved kernels in grs-sgminer.
Srcxxx removed the kernels in the open source and replaced it with the precompiled bin files (which are closed source). We have inspected these precompiled files to any harmfull code and all was good. All he wants is profit for his users and for himself (instead keeping it internally).
Fact is that his pool gives more coins/profit. It is his decision if he wants to release the whole code or not, we can not force him to make it all open source.
Feel free to ask any other concerns or give me a PM if you have any urgent questions.