From Justin.tv API Wiki
Most read requests to the REST API require no authentication. Requests to the REST API that write user data use OAuth token-based authentication. OAuth applications can be created in at the http://www.justin.tv/oauth_clients/list for developer users (in order to make your user a developer, please ask in the Google Group for now). Developers can request that an application be added to the Approved apps list, which gives the app permission some additional calls, including creating users and channels through the REST API.