That is definitely not "routine" pay for high school kids writing HTML in any year. Sounds like you hit a clueless marketeer who had been huffing the dot-com bubble.
Hacker News has a disproportionate population of people who work in fields and locations where you can easily expect to make six figures straight out of college, and as a result HN has some seriously skewed ideas about how much money is "real" money. When I got my first programming job (in the mid-'00s, in a town with a population of ~250,000) I made $15 an hour. I was absolutely delighted to get it, and it was enough to live well and save some money besides.
Of course, $22.60 in modern Seattle is less impressive, depending on whether he lives in the city proper or in the suburbs. But you can't expect tax-funded jobs to have the same kind of ridiculous salaries that Amazon and Google can afford to pay. And the guy's an activist. This has got to be a dream job for him--a chance to make a difference in something he's passionate about. Some things are worth more than money.
Yet, he developed a fair bit of software for this free already. Sometimes people do things for the public good. Plus you know he's going to be hired somewhere else after this if he wants to, and if he owns the software he develops, he can make bank.
I know Tim personally, since he contributed for years to the SageMath software project while he was in high school here in Seattle. He is an extremely sincere person, who care intensely about things (like open source software), and has little interest or motivation related to money. The potential that he could have any impact that could improve the terrible police/people interactions even a little in Seattle is I'm sure all he cares about. I very much wish him the best.
Whether or not he cares about his bank balance doesn't change what fair compensation is. If you frame this as "you can donate $10 to your favorite cause, or $50", the rate might seem more meaningful.
Still, people make far less per hour doing far more than basic front-end work today.
Don't get me wrong, I think he should make as much as he can get away with making, but 22.00 an hour really isn't scraping the bottom of the barrel for programming work in a lot of places, not even in the US.
$22 an hour for programming is definitely scrapping the bottom of the barrel in the US (unless you're an intern or trainee).
I live in a pretty cheap area of the US, and the only place I've seen jobs paying that poorly is on odesk (and most of these jobs are taken by people in low cost of living countries).
If you're working for $22 an hour, you're selling yourself short.
Uh, seriously? This is less than what high school kids routinely get paid to do HTML ($30/hr, and that was in the 90s)