I don't know anything about 'moss' but considering that the 'deprecated' library is being called the version you are using cannot be compatible with your version of Moodle. That is, it is too old.
The version in the plugin library is for 2.0 and 2.1. You are running 2.9!!
The github site has not been updated for four years and it says not to use it in a production site. Doesn't sound too optimistic.