ReactOS Portable Systems Group
A bunch of people very knowledgeable in ARM programming, also known as the ARM ninjas (AKA Code Ninjas).
Trained in the secret arts of ARM system programming in the depths of the internet, they are masters of the craft. From the shadows, they commit code that actually works (most of the time) and dare to approach the untouchable (the ROS memory manager). Their true identities are closely guarded secrets.
They are known for sharp, witty commit messages, often depicting various ReactOS code failures in a quite sarcastic way. Note that even they managed to get ROS a bunch of regressions, luckily fixed quite fast.
Some say they are from Apple, IBM or Google.