Yeah, you will be able to decompiled it (anyway, you won't get all of the files), but you really won't be able to add your edits to the compiled .jar again, so it's kinda useless, unless for stealing some codes as Tryskell said.
Rizel is a really good person, he even helped me with java when I was really in need of help. Anyway, I am a future buyer of these all events (package) and I'm going to give him extra money as a reward for his kindness.