Investigation on Jabber Servers

Sugar relies on shared roster groups.  Googling this resulted in a page from xmpp.org: http://xmpp.org/extensions/xep-0140.html

At the top was a red line of text:
WARNING: This document has been retracted by the author(s). Implementation of the protocol described herein is not recommended. Developers desiring similar functionality are advised to implement the protocol that supersedes this one (if any).


Well, that's bad.  Incredibly bad.  That tells you that required functionality will only be supplied by old or bizzarely maintained software.  However, there was a mercy on the page: 
the protocol described herein has been retracted in favor of XEP-0144: Roster Item Exchange
That is a draft standard protocol:
http://xmpp.org/extensions/xep-0144.html
I will study
1. How it differs technically from XEP-0140
2. Whether it could be modified to be backwards-compatible with XEP-1040
3. Whether it would be feasible to modify existing Sugar applications to work with XEP-0144 instead of XEP-1040