Sorry to nitpick. I am sure you know what you are talking about but people are easily misinformed and so definitions matter.
Chromium is Open Source. Waterfox is no more Open Source than Chromium.
Chromium is primarily developed by Google. So, you should be vary of their intentions and also aware of the potential fragility of a project dominated by one large player.
That said, Waterfox has exactly the same problems. As a fork of Firefox, it is dependent on Mozilla.