MIT/BSD licenses allow for proprietary forks. The most popular BSD-based kernel is Apple's, which isn't distributed under the BSD license. The most popular GPL kernel is Linux, which still is.

So with the BSD license somebody can take your work, improve it, distribute it under a proprietary license and supplant you in the market. Compare macOS or iOS installed base to FreeBSD.

But then the codebase is henceforth tied to that company. If Apple is dead in twenty years then probably nobody is still using the iOS kernel (and not because they switched back to FreeBSD), but if Google is dead in twenty years most likely Linux is still popular all over.

MacOS/iOS is not based on a BSD kernel.

https://imgpile.com/images/uL3CFP.jpg

macOS/iOS is based on a hybrid of the Mach kernel and the BSD kernel:

https://en.wikipedia.org/wiki/XNU

And Mach too is available under BSD-like terms.

It's important to remember it's not Free/Net/OpenBSD based, though, even if it had used bits and pieces from there to update its OSFMK derived kernel (OSFMK shared common origin point with NeXTSTEP kernel).

Arguably one can just call it Mach, as the bsd server part was delivered as part of Mach.

I was thinking more like:

- software written for a company has a lifetime ~ the life of a company

- MIT/BSD software may be adopted and not shared.

- GPL software would be shared widely and changes would be given back.

I'm just speculating and I have no idea what the real statistics are.