Also, quite frankly, looking back, it wasn't something that really is worth worrying about. First off, even if you're the smartest man on Earth, and you write something really interesting, it will take you years to do. In other words, it will take you time before it's really even worth stealing. So if you start making it public early on, don't worry about people and companies trying to steal your work. They'll probably not even know about your work, and they'll certainly not think that it's worth stealing. And by the time it is worth misusing, the project is already well enough known that people can't really misuse it on a big scale without getting caught. So the very openness of the process actually protects the developer to a large degree.
So have people used Linux without following the license? Sure. Copyright isn't necessarily honoured in all parts of the world, and there are nasty people and companies that just do legally dubious things. These kinds of things happen. But once the project gets big enough for those kinds of things to happen, there really isn't any point in worrying about them. The people who misuse the project limit not you, but themselves. If somebody uses Linux without following the GPLv2, they just limit their own market (they cannot sell it legally in the developed world without having to worry about the legal side), and they won't get the advantage of open source that the companies who follow the license get.
Which are the benefits of Linux for the users, apart from the fact that it's free?
The biggest advantage has very little to do with the money, and everything to do with the flexibility of the product. And that flexibility has come from the fact that thousands of other users have used it, and have been able to voice their concerns and try to help make it better.
It doesn't matter if 99.99 percent of all Linux users will never make a single change. If there are a few million users, even the 0.01 percent that end up being developers matters a lot and, quite frankly, even the ones that aren't developers end up helping by reporting problems and giving feedback. And some of them pay for it and thus support companies that then have the incentive to hire the people who want to develop, and it's all a good feedback cycle.
What's more important, Linux's huge user base or its large developer base?
I don't think of them as separate entities. I think that any program is only as good as it is useful, so in that sense, the user base is the most important part, because a program without users is kind of missing the whole point. Computers and software are just tools: it doesn't matter how technically good a tool is, until you actually have somebody who uses it.
But at the same time, I really don't think that there is a difference between users and developers. We're all "users", and then in the end, a certain type of user is also the kind of person who gets things done, and likes programming. And open source enables that kind of special user to do things he otherwise couldn't do.
Are those special users that actually do things more important? Yes, in a sense. But in order to get to that point, you really have to have the user interest in the first place, so a big and varied user base is important, in order to get a reasonable and varied developer base.