considering that all closed source miners almost certainly contain open source code or code derived from open source projects and is precisely how crypto assets have come to be.
So if it is like you say, why did you even have to ask me when it looks like to me you already gave the answer before making the question?
Also, it's a little strange that you suddenly came from your fpga threads here, with your licensing question.
So here is an answer i hope it will satisfy you :
I am not using copy pasted code from open source projects, but i am using some good ideas, reworked in my own style.
this is likely one of the reasons why you have had to close source yours
The reason is obvious, if you follow the open source scene (oh you do, you wouldn be here now if you didn't), then you know that there are always 'good helping people' who remove the devfee, compile, upload and share on forums the 0% fee version.