mps-youtube does not use avideo/youtube-dl as backend, it's just a
simple wget script. Therefore, it is not youtube-dl, but it still
manages to avoid JS. You can easily tell because it barely wowrks: half
the vids don't play because no JS.
As with anything in the FLOSS world, the simplest way to know if
something contains proprietary software or not is this:
If it looks bad and half the functions are broken, it's 100%
libre.
If it looks good and functions very well with a modern UI, audit
the code ASAP.
