Martin Korth (the man behind the emulators) is a bit of an ass though. NO$GBA was the perfect example. He told everyone he'd made this excellent, small, fast, accurate emulator...
and you can't have it!
He brought out two demo versions. One had sound but no colour, one had colour but no sound, and neither had cartridge emulation, meaning all emulation had to happen in RAM from what would be via link cables in real life. The full version cost an obscene amount of money and was meant only as a development tool.
He declared this to be a form of protection that could not be defeated, which resulted in someone managing to combine the two demos and hack in cartridge emulation. Martin called this a piece of crap, but responded anyway, by taking down all NO$GBA downloads.
This remained the situation for a while, until he finally did what I would've suggested he do in the first place. He released a 'free' version (full emulation, no debugger, with a cheat function), a 'demo debugger' version (restricted emulation, partial debugger, no cheats), with purchase options available at various prices with various functions. This gave the kiddies what they wanted, and meant they wouldn't attempt to hack his demo versions any more.
Frankly, I think this ended up about as good as could be. Martin may have had the right to do what he wanted, but dangling an excellent GBA emulator in front of the community while denying everyone access was a masterclass in how to be an ass. The kiddies burned him for it, and he ended up having to give them what they wanted in order for them to leave his demos alone. We got a great emulator out of it, and he gets to give his clientèle the demos they want without fear of people hacking them.