How is that extortion? If you use a library/project with a licence you need to abide by its terms. If you don't want to do that, then either write it yourself or find an alternative. People asking for the source code is not extortion, they're fully within their rights to do so.

I actually found the anecdote I was referring to:

https://news.ycombinator.com/item?id=44605873 (see comment by user yalok).

""" Just anecdotally, but this aligns with my observations on the trend/growth of successful useful open source projects that go with permissive BSD-like license. ~20 years ago there were way less of those than now. And as a SW developer doing client side/apps as well, using GPL/LGPL is a total pain and basically cost prohibitive, unless I work on my personal small project where I don’t care about having to/risking to open source the rest of the code and getting sued/cloned… Real life example from ~2010 - we ended up including an LGPL library in our mobile app code, and published/upstreamed all the modifications we did to that code (mostly ARM optimizations). Once the app became popular, our competitors came to us demanding the source code of our app - just because iOS didn’t support dynamic libraries (so we had to statically link it), and giving them the object code to relink it wasn’t enough for them (which would satisfy the spirit of LGPL), because they really wanted to see how we hacked around iOS camera input APIs… """

Arguably the competitors didn't have a case as the object code was provided, so I would stand by calling this extortion. Maybe the legal burdens were too high, so the company complied.

I didn’t even realise that was a possibility with iOS. Thanks!