1) OWIN is based on RFCs 6749 and 6750 (oAuth 2.0 and Bearer Tokens), and whilst I can't say for certain that it's 100% compliant in every respect, that does certainly appear to be the goal, there's an interesting discussion on similar matters on the Katana forum here.
2) Have a look at this, it's the Azure AD Git sample for WSFederation, recently mentioned in Vittorio Bertocci's Cloud Identity blog here.