Does MultiSite Login work with PostgreSQL?

You would be the first PG tester. I'd be happy to work with you to tweak queries to get them functioning. I did a quick scan and here's the only ones that I can see that might be a problem (Though I've never actually used PG, so I wouldn't know for sure):

Not sure if this sub-select will cause problems:
db_query('DELETE FROM {multisite_login_sessions} WHERE sid NOT IN(SELECT sid FROM {sessions});');

I'm not sure why I have the backquotes in this one but that will break PG:
db_query('SELECT s.sid, s.uid, s.hostname, s.timestamp FROM `'. $other_db .'`.sessions s WHERE s.sid = "%s"', $sid)

This one might need to be written in long-form:
db_query('INSERT INTO {multisite_login_sessions} (sid) VALUES("%s")', $sid);

I don't think PG can do REPLACE. This one is in hook_enable:
db_query('REPLACE INTO {multisite_login} SET uid = %d, pass_hash = "%s"', $uid, $pass_hash);

If you can run those in isolation and see which ones work and which ones don't, then we can alter accordingly.

Regards to your "can PG do multisite" question I found this page here:
http://drupal.org/node/45332
http://drupal.org/node/290768
your Google skills are probably better than mine.

I reworked the queries that I know for sure would not work. For the others I'll need someone to try it out who uses PG.