It probably does what it claims it can do and it's nice that it's reviewed by Mozilla. However, it can't provide the basic service that it claims that it's designed for, unless the user installs additional software and in my opinion, it's kinda shady that they didn't mention this on their add-on info page. So I removed it without trying further actions.

Should definitely be up front regarding additional required dependencies. Especially when most of the other similar add-ons do mention it. It's almost like, they're hoping to catch a few extra downloads from people who're looking to avoid the additional "helper" executable.