Actually I think the code is pretty good
Definitely not stolen.
I think Mark answered pretty well why. The Crypt.dll does a little "authorization" with Razor before it will let any data through. Allowing people to take Razor and make their own seems like sort of a bad idea. And I think it is very significantly easier to take the Razor C# and make a few mods than to start with Injection and make something that is usable. I'm probably being paranoid, though, I admit that. If Injection was sufficient for someone to build their own Assistant tool, wouldn't there be more of them in existence now?
There is another reason, and that's there were a couple of different "Cheat detection" methods used by the real UO servers and by UOGamers which have code to deal with them in Crypt.dll. I don't know if any of those methods are still in use, but removing them from Crypt.dll is non-trivial, and we wouldn't want to expose those methods if they're still in use today.