Hi !!
I can confirm, that the Courier support has top priority. The project was started just to fit my personal needs and I didn't know that other IMAP servers act different as mine does. Since this is still an early alpha version, we cannot guarantee full support for all servers (haven't tested them yet).
Now I have access to a Courier server and have to change the behavior of the imap_root property from the ground up.
I also have a courier-imap server, the cvs version works fine without any modification as far as i have tested it (really not too much). I can help in anything you want.