Great. Going step by step to the point. The point is that GPL license was created by very bright people, clever enough not to prohibit something that can not be enforced: distribution of binaries over private channels without source code. You can assume that I'm asking djm34: "Hay djm, please look at this source code, please compile and make it faster for me, I will pay You 10BTC. I don't need source code and I will not publish binaries, because I know that I will have to publish source code too, that costs 100BTC to buy it from You. Thank You." No license break.