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Presumably illegal in the sense of https://en.wikipedia.org/wiki/Criminal_transmission_of_HIV (and note that in some jurisdictions "exposure", not just "transmission" is criminalized, per that wikipedia article).

Except you can decide if you want HIV status to be displayed and the last time I mucked with my profile, it was optional anyhow.

Its not even clear if whats being sent to the analytical companies is whats displayed in the profile or all fields even if they are not displayed.

I believe in certain places that if you withhold the information of being HIV positive from someone you have sex with and infect them, it's a pretty serious crime. I think it might even be a crime if you don't infect them.

Depends on the state. The majority of states either have laws relating to disclosing known STDs or laws specifically about disclosing known HIV status, or both.