Here are some notes I've made in the process of hacking around in the internals of AtheOS
Please correct me if I'm wrong; all this info has come from looking through the source in the process of trying to understand the OS, and so will miss out anything I wasn't too interested in at the time.
On using the filesystem for everything (and a complaint about the SNR of the mailing list :-)
Don't delete the Application object!
Here is a message from Kurt to Tord Janssen on the topic. It also has some suggestions as to what to do when your programs crash, and a reason that the entire desktop might hang when a program dies.
Kurt to Phillip Pearson on the viability of a VNC server for AtheOS