My reason for doing this is entirely selfish – I don't want to have to think about Pinline anymore. It never sold well and it didn't get much press for the simple reason that it is not very good. I've made a number of false starts on a second version but ultimately it just isn't what I want to spend my time and attention on anymore.
Still, it would feel wasteful to just pull the plug entirely. If you liked Pinline and want to improve it or you're a newish iOS developer wanting to take a look at a medium-sized project please feel free to fork the project and poke at it. Like any good developer I tend to hate the code I wrote last week – and Pinline's last update was last year so if you see something really dumb in the code please be kind enough to assume that I know it's dumb and would do it differently today. There are warts and hacks and some of them are really ugly but I will say this in my defense: those warts shipped and those hacks worked. I'm proud Pinline got that far.