UPDATE: use bz.js instead!
The API docs are here as well as a link to download: bugzillaRPC. Because the library makes HTTP requests to the Bugzilla server, you can’t use it from regular content. You can however use it from any extension or chrome-privileged code. One thing we had hoped to have was account creation functionality. Unfortunately, a user with ‘editaccount’ privileges must be logged in to create an account for another user. This is a security hole for our project, but there is functionality for offering a user an account by sending them an email. I didn’t implement every function in the Bugzilla Web Services API, mainly the ones the project uses, but it’s extremely easy to extend. We hope other people can use this!