The GPL does put restriction on use. If you make modification to the code and do not share those modifications, you are constrained from using the code you modified.
And those constraints are for political reasons. The Four Freedoms are a political ideology about how software, developers, and users should morally interact, and the GPL exists as a legal tool to support this political ideology.
Edit: clarification - by "use" here, I'm including "bundle it into a black box of hardware and sell that hardware."
No, it does not. It places restrictions on redistribution, not on use. You can use it no matter who or what you are.
> If you make modification to the code and do not share those modifications, you are constrained from using the code you modified.
Incorrect. You can modify and use it to your hearts content. You are only required to share your modifications source if you distribute the modified software.
That's wrong. It's only if you distribute the software you modified that you need to share those modifications. If you dont distribute it, you can use it without any restriction at all.
> The GPL does put restriction on use. If you make modification to the code and do not share those modifications, you are constrained from using the code you modified.
This is is only true if you consider distribution as part of "use". You're fully entitled to privately run modified GPL code, even as a server or whatevs if it's not AGPL.
You are mistaking open source with free software. You can put as many restrictions as you want and still have open source. Open source just means you provide source with your product.
And those constraints are for political reasons. The Four Freedoms are a political ideology about how software, developers, and users should morally interact, and the GPL exists as a legal tool to support this political ideology.
Edit: clarification - by "use" here, I'm including "bundle it into a black box of hardware and sell that hardware."