That's because you're looking at the raw bytecode for the mod, not the source code.
If you wanted to read .class files as code, you'd need to decompile it first (fortunately Java is an open source format, albeit complicated).
Or you can write it as a mod, as diesieben suggests.
Decompiling sounds interesting (but another learning curve). Making a mod sounds a bit more interesting. Only made one unlaunched bukkit mod before so playing with forge sounds like a cool new hobby.
Now we're talking. Is there some sort of get all items and blocks from the registry function? I can see that I can search for one as of now. Miiiight not be a good idea to cycle through all possible a-z0-9 variations.