Drupal 6 with custom OAuth Server Quick question, 
Has anyone made their own OAuth server and then tied drupal logins into it? 

My boss is asking me if it's possible to run our own internal OAuth server that we can use for multiple things, mobile app, internal app and our website. but they don't want to use the drupal site for the oauth service.

Everything i've found so far is a module that lets you use OAuth in drupal but it makes drupal the OAuth server instead of having Drupal hit an external oAuth service.

Any help would be appreciated.
Drupal 7 has the oauth2_server module that allows you to run an OAuth2 server. It is well documented and integrates a well known and stable PHP library.
OAuth2 is probably a better option for you than OAuth1 because it has grant types optimized for different usage scenarios (mobile app, web app, etc).

If you're limited to Drupal 6, your only option is the OAuth module (also available for D7), but keep in mind that Drupal 6 is basically a deprecated version so when it comes to contrib support and bug fixes you are pretty much on your own.