1) There's no branding on the shirt at all. The shirt is shipped from Scalable Press, so I'm not sure what the packaging will say, but I imagine they have something in place for white-labelling.

2) "Passive income" side project, though with all the HN hate it's turning into a bit more scrambling than I'd imagined :).

3) I do ask them questions since I'm a pretty early user of the API, but it's pretty well-documented at this point so I don't imagine you'd run into much trouble developing on it.