Your cursory search likely provided outdated info. [0] Quoting from it's maintainer: [1]
Waterfox is independent again: [0]
And System1 are an “ad-tech” company but the term should be used loosely. The ownership made sense as they are a search engine aggregator and they own a bunch of old school search engines like DogPile, InfoSpace etc. Nothing to do with what people associate ad-tech with, i.e. tracking you across the web or collecting personal data.
[1] https://news.ycombinator.com/item?id=37435511