What "anti-features" are there?

[FinixFighter]

F-Droid says that the app has an Anti-Feature, in particular it says that "this app promotes or depends entirely on a non-free network service" (source: https://f-droid.org/en/packages/com.odysee.floss/).
Some users, including me, wonder what does it mean; could it be possible to have some explenation?

I take the opportunity to say thank you for your work!

[licaon-kter]

@FinixFighter https://f-droid.org/docs/Build_Metadata_Reference/#AntiFeatures