WordPress MU

We are trying to use wordpress for our tech project (with ~70 users) both for the purpose of blogging and for our main website.

We currently automate/control access to our svn repositories (and trac, buildbot) and I'd like to be able to extend this to wordpress (otherwise, we'll need to consider another option).

The users are in both a 'flat' space separated file, and in a postgres DB (we store the username and md5 of the passwd) ... how does wordpress handle users in it's innards? Are they stored in the MySql DB or are they in a 'htpasswd ish' file?

Could I hack something up? Where should I start with this? If anyone else is interested I'd collaborate, or take advice on turning this into a plugin (possibly taking other forms of mass edits like csv etc.)

They are stored in the databse.

Are you looking at single WordPress or WordPressMU?

Right - we are using single Wordpress not MU. I didn't catch the difference when I googled for wordpress info.

Should I re-ask this in the single user site?

You'll get more specific answers, but still - the user passwords are stored in the database in both cases. MD5'ed as well.