From Halopedia, the Halo wiki

A developer is an user that has access to certain database functions in order to manage the site. They also have the same abilities as an administrator and bureaucrat.

How to become a developer?

While rarely given to another user, the developer user group is reserved for the owner of the domain, and the person who hosts the site. Anyone else who holds this role is up to the discretion of the current developer.

Meet the developers!

If you need to contact the developers, you can do so on their talk pages or social boards.