Sharing for advancing humanity / benefit of society, and megacorps getting rich off it, is not either-or. On the contrary, megacorps are in part how the benefit to society materializes. After all, it's megacorps that make and distribute the equipment and the software stacks I am using to write code on, that you are using to do your research on, etc.

I find the whole line of thinking, "I won't share my stuff because then a megacorp may use it without paying me the fractional picobuck I'm entitled to", to be a strong case of Dog in the Manger mindset. And I meant that even before LLM exploded, back when people were wringing their hands about Elasticsearch being used by Amazon, back in 2021 or so.

Sharing is sharing. One can't say "oh I'm sharing this for anyone to benefit", and then upon seeing someone using it to make money, say "oh but not like that!!". Or rather, one can say, but then they're just lying about having shared the thing. "OSS but not for megacorps/aicorps" is just proprietary software. Which is perfectly fine thing to work on; what's not fine is lying about it being open.