I have first heard of Terry Davis on HN. I am not American, so I couldn't probably do much. A lot of comments blame mental illness etc, whereas IMO, his condition being well known, an otherwise talented person like him should have been more taken care of by his relatives and anyone who was in capacity to recognize his good parts. So much people knew about him and him being so unique I thought someone would support him somehow.
As I understand it, some people did. He was living with his parents at one point, and had family support to at least some degree. Mental illness is tough sometimes...it's not always possible to protect an adult with mental illness from themselves (and it's not always safe to welcome an adult with mental illness into one's home or allow them to remain if their mental illness proves dangerous).
There's a lot of discussion we, as citizens in the US, should have about safety nets for people with mental illness, and I think it's clear Terry wasn't getting the help he needed. There are homeless folks in every major city in America who are similarly dealing with mental illness, we just don't hear about them because they aren't brilliant programmers working on such an odd project that it almost demands attention from fellow nerds.
We have no idea what hardships Terry's family dealt with. He was certainly brilliant, but not always kind or calm. I've found him fascinating for years (in a sort of "there but for the grace of god go I" sort of way, as severe mental illness runs in my family), but he could be incredibly hostile and unpredictable (in addition to the overt racism that ran throughout his work and words). He was banned from HN numerous times (someone linked an HN profile of his but he's had several) for his hostility and racism. I'm not saying this to speak ill of the dead here...it just seems awful to blame his surviving family when we know so little about what went on that led to him being homeless. I don't know that they'd ever see it, but it's still kinda shitty to blame someone's family for not doing enough, especially when we don't know anything about them or what they did for Terry.
I have followed Terry for a few years now and from my limited understanding he had a lot of support from family. He lived with his parents and while taking medication he was "okay" however he was a grown man and unless hospitalised there is no forcing him to take his medication. I can recall a number of times he clearly came off his meds and went off the rails. He has said both that his parents kicked him out and that he left because he wanted to. It was very hard to know what was true and what was the illness with his rants.
The sad truth is that while he had family that cared about him that wasn't enough. He should have been hospitalised imho.
He was supported by his family. I'm sure you understand that receiving support doesn't make mental illness disappear. And in the US, no one can force him to take meds unless it's proven in court that he is going to harm himself or others.