Distributing software is something you "do" with the software. If I meant restricting the use of the software I would have said restricting the use of the software.

The GPL doesn't restrict distributing software. Copyright does; without the GPL, you would not be allowed to copy the software at all, due to copyright laws that cover all creative works from the moment they are created, regardless of whether anyone opts in. The GPL grants you additional freedom to distribute the software, as long as you follow their rules.

Now, it doesn't grant as much additional freedom as, say, the MIT license, but the only freedoms it fails to grant you are the freedom to take someone else's freedom away. You can do anything you want with the software, as long as you don't do something that limits someone else's freedom to do the same.