OpenAI is a 501c4 not a 501c3. Also the structure is much more complicated for OpenAI.

Nevertheless the point stands - I don’t see what relationship company organizational mission has with their technical responsibilities. Indeed, if the open sourced everything, standing up a clone would be easier which creates funding risk due to a race to the bottom of people who didn’t invest into the R&D investing very little additional to compete.

Non profit doesn't necessitate open sourcing their whole product. If you don't like that, don't donate. As long as they are transparent about their decisions that is the only obligation they have.

Yes

"open" is literally in the name, so yes