If the public are paying for it, then it becomes a subsidy.

And good luck getting the US government to require the code to be GPLed. That’s even less likely to happen than a public subsidy for OSS at all.

They typically do the opposite and require “commercialization” to ensure the benefit of the publicly-funded technology is captured by their donors.

This is how it basically works in biotech, for example. Government grants to study the medicine and then when the scientists actually find something important it becomes a “public-private partnership” often without even a royalty for the public let alone making it a public good.

That’s not how government funding works in a modern democracy, unfortunately. It would amount to a cash transfer to big tech to make the public pay their R&D costs.