hi KG,
Those are two separate issues.
As far as a Peer Connection is concerned, all is video stream , wether you got it using GUM with your webcam, or using GUM with "screen" (or "tab"). The capacity to relay a remote streams is addressed in bug #383. The day it will work, it will work with your screen sharing as well.
Now, screen sharing is a chrome only feature as this stage. It has some serious security implications (thanks eric for pointing them to me in the first place):
This is google's position as of august 20th (from j. uberti) as to wether screen sharing should be in webRTC 1.0 or not:
""
Because of the security concerns, the current direction is to require use of an installed component (e.g. Chrome app/extension or the firefox equivalent) to activate the screen sharing functionality. We will evaluate how this goes, but at current time there is no plan to expose this functionality to the drive-by web as part of WebRTC 1.0.
""
Then, you were speaking in some of your other e-mails about remote modification of document or document sharing as in "editing a remote document" and not "displaying remote documents". This is not in the roadmap of webRTC (AFAIK), but you could look out for implementations of VNC/RDP in JS to get everything you want at the application level.
HTH.
alex.