

This is one of the old-time original arguments in the OSS community.
The crux of the matter is that the GNU licenses require that modifications be released back to the community. Other “more permissible” licenses like MIT do not.
So if you want to make a commercial version of X, and X is under a GPL, then any changes you make need to be released under the GPL. The idea being “I shared this code with the community with the intent that you can use it for free and modify it as you like, but you need to share back what you do.” Also called “Share and share alike”.
This defends against “embrace, extend, extinguish” tactics that companies like Microsoft has loved to do. They can’t take your code, modify it for their own purposes and re-sell it possibly making a more popular version that is now proprietary.
You high?