I've been thinking lately on what would need to be open sourced (UI) and what we could leave behind (Kernel).The Workplace Shell is OS/2. It's still a technology that no ones has. This part (Workplace Shell) needs to be freed through rewriting it. Needs to be more stable. It's a biggy but it could be replaced class per class (smaller tasks).
MMPM/2. It's old and probably very buggy. Also needs to be rewritten and updated.
Then there is PMShell, the Core of OS/2. It's probably the most complicated part found in this operating system.
About the license. I'd suggest GPL and LGPL for linking and commercial purposes (where it's logical).
Anyone else got ideas?