Copy left is like the Robin Hood of the copyright world. Basically, it’s a type of licensing where, sure, you can use, modify, and distribute the copyrighted work, but there’s a catch. You have to give the same rights to anyone else for any derivative works. So, if you modify the work, you can’t just slap a new copyright on it and restrict its use. It’s a way to ensure that the work stays free for everyone to use. It’s pretty popular in the open source community. It’s like copyright turned on its head, hence the name “copyleft”.
This argument reminds me of the Tolerance Paradox described by Karl Popper, who stated that in order to maintain a tolerant society, the society must retain the right to be intolerant of intolerance.
In the licensing context, yes, the Apache and Expat licenses may grant your users the freedom to create proprietary software out of your works, but at the cost of sacrificing all the basic freedoms of all the users that will use the derived non-free product.
So, like Popper said that you should prefer removing the "smaller" freedom for a society of being intolerant in order to guarantee the "greater" one of remaining tolerant in the future, since you still have to choose which freedoms you are going to negate, it's preferable to use copyleft and impede the "smaller" freedom of creating proprietary software than not using it and allowing the crushing of future users' fundamental rights.
GPL is so free that it conflicts with other versions of GPL because this version wants to prevent you from restricting freedom and that other version tries to restrict your freedom by preventing you from restricting freedom.
It's really easy to detect duplicate programs. I've failed multiple students due to cheating on assignments. Code obfuscation is incredibly easy to detect using something like MOSS .
Code web app class homework assignment. Put a link to the AGPL on the main page. Let another student access the main page from their personal smartphone. Give them a copy of the source code. When professor accuses you of helping them cheat, you can tell the professor you legally had to.
I know this is a joke, but assuming you're the author, then you're under no obligation to follow the license. Only people to whom you transmitted the code are bound by its terms.
If in my hypothetical, I'd used the GPL rather than the AGPL, or if I'd neglected to let the other student access the main page, you'd definitely be right.
But AGPL is basically "GPL but also accessing the software over a network counts as distribution."
So, if I let you access my AGPL software over a network, I've granted you the right to demand the source code from me, just as if I distribute a compiled executable to you under the GPL, I've granted you the right to demand the source code from me.