An open source foundations with billions does not exist, except Mozilla Foundation but they don't really spread out the money to other projects compared to what they spend on their own products.

So, the answer is that nothing exist.

Out of the given options a few also don't qualify (like I mentioned, Apache for sure, opensource.org most likely) because they don't spend money on software development at all.

The original comment of mine that started this thread:

Why isn't there a public open-source fund [...]

I know it doesn't exist. The non-existence thereof was what prompted that question. I have no idea what point you're attempting to make.

Clearly you are smart enough to realise what point I was trying to make, although it was perhaps tangential to your original question.

I do apologise for replying to you. If only HN would have a feature to block me from replying to you in the future.