I'm very surprised to see that Steve has approved an open-source modding project. My recollection from the author of AuroraMod was that Steve did not approve of open source mods and when the author retired the mod it would be up to Steve to allow someone else to take over the mod and have access to its source code.
I can't speak for Steve (and I welcome his input here), but based on our discussions, this is why I think he's OK with people using the open source AuroraPatch versus allowing people to work with AuroraMod:
AuroraMod consisted of a deobfuscated and decompiled version of Aurora. It was essentially a messy and convoluted version of the Aurora source code, modified, then recompiled into an executable.
Someone contributing to AuroraMod would effectively have access to the entire code base (albeit not pleasant to work with).
I can see why this is scary from the point of view of Steve as it increases the chance of someone stealing the code and working on their own fork (granted that would be a lot of man-hours and be very bug-prone).
AuroraPatch on the other hand doesn't exist or make any sense without Aurora. It doesn't expose any of the source code of Aurora itself.
Instead of having an overview of the entire code base (like AuroraMod), it's like having a magnifying glass that allows you to look at the execution state of the application at certain points in time.
No deobfuscation or explicit decompilation is done.
That's my take on it anyways.