I'm pretty sure that wouldn't work. HN is the product of a rare set of initial conditions, and the funding aspect is a critical aspect of that. The symbiosis, if you like, between HN and YC is part of the DNA of both entities. No doubt it has some downsides (such as job ads on the front page), but I'd say the downsides are small enough that it wouldn't be worth the risk to try to minimize them further. Of course that's just my opinion.
Karate is open-source and will remain so. The IntelliJ plugin and Studio SaaS mentioned in the OP description are optional and you can find the pricing on our site.