To be a little more specific. Non-free (aka proprietary, aka the opposite of free and open source) software is not allowed on the official f-droid.org reposiory. Most trackers are non-free. That's why they violate our policies and have to be removed, or they would prevent and app from being published. FOSS trackers are allowed, but will be tagged with the tracking anti-feature warning. However, those seem to be rather rare.

This only applies to apps from F-Droids official f-droid.org repository. On 3rd party repositories all bets are off! (Basically all F-Droid compatible repositories other than the one provided by our team on f-droid.org) Apps in those can contain trackers or worse and may also omit setting appropriate anti-feature warnings.