https://en.wikipedia.org/wiki/Allan_Border Is a pretty famous cricketer.

That was my first thought too! but then realised Allan Border has a double L, while the app's name is "Alan"

I think it’s a reference to Alan Dye, who screwed design and usability of xOS 26 so epically that an app like Alan became necessary.

In reading more from this guy's blog, he also wrote a game called "Steve".

https://stevethegame.com/

Has he also written a Dan?

I believe it's named after a guy who likely influenced the direction of the macOS UI such that this app's development was necessitated in the first place.

Maybe derived from “a line”?

As an Aussie, I assumed it was a reference to: https://en.wikipedia.org/wiki/Allan_Border

My understanding it's a reference to Steve Coogan, who played Alan Partridge, who in one episode sees a friend called Dan, and starts shouting his name, but Dan doesn't react. Alan proceeds shouting: Dan! Dan! DAN! and eventually gives up. This scene was later parodied in a BBC programme about animals, where one animal shouts Alan! Alan! ALAN! and then realises the name's wrong: STEVE!