The size and quantity of companies working on things related to a project determines whether a strong copyleft license or a permissive license makes the project more successful
Say you want to make a business around a FOSS project. Which license should you choose for that project?
If your business starts gaining traction, people may realize it's a good business opportunity, and create companies that compete against you.
I'll simplify to two licenses, GPL and MIT. Then there's two options, based on which one you chose originally:
1) If you chose the GPL, then you can be sure that no competitor will get to use your code without allowing you to use theirs too. You can think of this as protection, ensuring no other company can make a product that's better than yours without starting from scratch. Because everyone is forced to publish their changes, your product will get better the more competition you have. However, your competitors will always be just a little behind you because you can't legally deny them access to the code.
2) OTOH if you chose MIT, a competitor can just take your project, make a proprietary improved version of it and drive you out of the market. The upside is if you get to be big enough, you can do exactly that to _your_ competitors.
You can see that when you are a small company the benefits of GPL outweigh the cons, but for big ones it's more convenient to use MIT or other permissive licenses. In fact, I think the answer to your question "why is the use of GNU GPL licenses declining?" is because tech companies tend to be bigger than before.
Now say you want to make a business around some already existing software. And say there's two alternative versions of that software, one under the GPL and one under the MIT license (for example, Linux and BSD). Which one should base your business on? And contribute to? Well, it's the same logic as before.
The size and quantity of companies working on things related to a project determines whether a strong copyleft license or a permissive license makes the project more successful
Say you want to make a business around a FOSS project. Which license should you choose for that project?
If your business starts gaining traction, people may realize it's a good business opportunity, and create companies that compete against you.
I'll simplify to two licenses, GPL and MIT. Then there's two options, based on which one you chose originally:
1) If you chose the GPL, then you can be sure that no competitor will get to use your code without allowing you to use theirs too. You can think of this as protection, ensuring no other company can make a product that's better than yours without starting from scratch. Because everyone is forced to publish their changes, your product will get better the more competition you have. However, your competitors will always be just a little behind you because you can't legally deny them access to the code.
2) OTOH if you chose MIT, a competitor can just take your project, make a proprietary improved version of it and drive you out of the market. The upside is if you get to be big enough, you can do exactly that to _your_ competitors.
You can see that when you are a small company the benefits of GPL outweigh the cons, but for big ones it's more convenient to use MIT or other permissive licenses. In fact, I think the answer to your question "why is the use of GNU GPL licenses declining?" is because tech companies tend to be bigger than before.
Now say you want to make a business around some already existing software. And say there's two alternative versions of that software, one under the GPL and one under the MIT license (for example, Linux and BSD). Which one should base your business on? And contribute to? Well, it's the same logic as before.