It's not actually free.
Unless you pay $30, it'll leave a big QR code watermark on the corner of the video.
Now, the listed premium feature seems to be media conversion, but I just download Video from Facebook normally without telling it to convert to anything - just download it as-is. turns out it still leave a big watermark.
I think $30 is too much for something like this.

The settings page for this addon is also too long as if it is made to deter user from configuring, and not much categorization is present.