Not read the thread properly so maybe someone already mentioned this but its not really possible to protect software if you want it to run stand alone, someone can always crack it if they are willing to spend enough time and effort. I suppose the question is, is anyone really interested enough to spend time cracking your protection.
I saw a link a while back about DRM http://arstechnica.com/information-tech ... pi-oh-yay/
I was playing with using DMA and VC programming to scramble and reassemble code into memory based on a key and the pi mac address that would change the encrypted code everytime it was run, but as this thread says its just obfuscation not really full protection. Nothing in life is certain, so, why not just give your software away anonymously its much less hassle and responsibility.