Why would they do that? Numpy gave it to them. It's theirs now. "Screw you nerds" is their opinion. Don't like that? Then dual license. Copyleft and a commercial license. They can pay, break the law, or go leech off something else.
Sounds a little schizophrenic to complain about the (lack of) money at the same time?
I personally think this may be connected to the "academic" origins and mindset of much OSS. Everything's "free" in that world, which can make a software's transition into the world with real economic constraints and sustainability challenges somewhat painful.
On the other hand, the GPL wouldn't make a difference here unless they are actually distributing it and my understanding of LGPL means that they could do whatever they wanted to as long as they use NumPy and don't change it.
Consider: today I might be working on FOSS. But maybe tomorrow a friend asks me to help him with his (small) business, by e.g. adding a little bit of automation. Suddenly, all my knowledge and experience of GPL-ed libraries goes to waste, as I won't be able to use any of that to help my friend.
Given two equivalent libraries, one on GPL and one on MIT, I'll always go for the one on MIT. MIT, BSD, etc. seem to be the libraries that give you most options (I'd say freedom, but that's not how GPL sees freedom) while still maintaining the integrity of the library itself. Those are the licenses that best and at the same time satisfy the needs of developers who are not in it for money, and users who don't want to waste their brain cycles on going through possible legal scenarios around all their actual and imagined use cases.
But the discussion here is about FOSS sustainability from the dev perspective, not yours as a user. Dual licensing was one option, proposed by the OP.
Or do you think it's OK that critical libraries like NumPy, Django, etc end up with scraps (if lucky), and then we read odes to that on HackerNews? Long-term planning needs a certain reliable continuum (no pun intended) of people and resources.
You know, experts able to meaningfully contribute at this level (core NumPy, core Scikit-learn, core Django, whatever) have very real trade-offs to make, regarding the cost of their labour, free time, family time etc, once out of academia. The "I HAZ BUG PLS FIX NOW, GIMME GIMME FREE" users are only one piece of the open source puzzle.
I'm sure your friend that runs a business understands this very well (or he'll be out of business quickly).
The presented reasoning may indeed be a big part of the problem here. I'm just describing it, not encouraging it. I am definitely not happy to see so much open source being used as critical components of worldwide infrastructure and businesses, and yet receiving little support both in terms of money and professional effort. FWIW, I do donate the little spare money I have to open source projects.
Beginnings are a creative effort, undertaken by passionate pioneers (rarely in it for the money), with outcomes that are notoriously hard to predict in advance. The hallmark of academia.
That's why I said the later transition hurts -- it's a conceptual and cultural shift, not merely financial.
Help me understand this please. In what legal way is GPL obstructing you as opposed to say an MIT or a BSD license.
GPL license has noting against use in a proprietary setting, its only if GPL'ed software is being sold/distributed, that it is required that the source and the changes be made available as GPL. Google uses GPL'ed software all the time and is far from the only one.
Which one? 2 or 3?