Without IP, what stops people incorporating GPL code in their closed source proprietary products? See you can't have your cake and eat it. Either you believe there is a thing called a license which travels with your product and binds the user as to how they can use it, or you don't, there isn't really any middle ground there. The alternative is "everything is public domain!" in which case, no GPL.
There are four freedoms that every user should have:
the freedom to use the software for any purpose,
the freedom to change the software to suit your needs,
the freedom to share the software with your friends and neighbors, and
the freedom to share the changes you make.
The GPL is a clever legal "hack" to achieve this, by allowing the code to be used only by others who agree to play by these rules. If the law were changed to enforce these rules directly, then no GPL would be needed. And eliminating intellectual property law restrictions on the use of code would get almost all the way there. (Companies would still be free to "protect" their code through secrecy: releasing only the compiled version and not the source code, but decompilers are pretty darn effective.)
"This is exactly what the GPL is designed to avoid."
...sort of. Source code access is important, sure, but here are a few more important issues that are basically orthogonal:
* The right to redistribute software
* The right to modify software (without source code?!?! Sure; imagine if I took Windows, removed the license protection code, and distributed that copy to you).
* The right to use software -- this, incredibly, can be a problem:
There is, in principle, nothing preventing us from applying "if you are distributing software, the source must be made available to your customers" to all software directly in law rather than through hacking copyright.
Or we could create a new system, one not based on the idea that you can own math and poetry, one not based on promoting the interests of publishers, and one that instead encourages the sharing of source code. The GPL is just a way to establish such a system by using the existing approach. There is no reason why we could not scrap copyrights (at least on software) and write a law that codifies the GPL more directly -- say, that any software user has the right to request a copy of the source code for their software.
I'm not saying it is a realistic possibility in today's world, but it is not as though the copyright system is the only system we could have.
> Without IP, what stops people incorporating GPL code in their closed source proprietary products?
Nothig. But then, a company wouldn't have the entire governemnt's power to persue and extract money from people using their software. It's a completely different equilibrium, you can't just look at one side of it.
And I'm not saying it's a good thing either. Altough I defend that it's not smart to depend ("depend" excludes games, by the way) on proprietary software, I never tought it was immoral to create it, until the NSA scandal. Now I don't have any firm opinion about it.
> Without IP, what stops people incorporating GPL code in their closed source proprietary products?
You can do this even with IP... if you're building SaaS instead of shrinkwrap, due to the GPL's most relevant restrictions here all hinging on the act of distribution of the actual software.
