I've had the idea kicking around in my head for some time for a blending of Free Software and commercial software development. While I feel that the standard models of intellectual property are inherently flawed, fixing them is a utopian ideal that can only be reached in tiny, incremental steps over a long period of time. Realistically, there has to be a bridge. I think the GPL is great, but the free redistribution to anybody aspect is a stumbling block. I understand and agree with the other freedom arguments, but I don't see how that contributes to a user's freedom.
The Walled Garden License (WGL, or "wiggle") is dirt simple. Take the GPL. Add the restriction that redistribution is limited to the community of users that you, the software developer, have defined. Voila. Within the garden, you have all the freedom of the GPL. Anybody can write and distribute patches. Everybody gets the source. Nobody is held hostage by the original developer. Nobody gets in for free (unless you want). And membership is irrevocable.
This opens up some interesting possibilities. Once someone enters the community, they can compete with the original developer for customers. The community is not tethered to the original developer; if they neglect their duties or take development in an unpopular direction, the community can still survive. Beyond providing an insurance policy for the customers, it also gives an impetus to the original developer to continue progressing. A conventionally-licensed software package is really better viewed as a monopoly of one. Microsoft Word theoretically competes in the word processing market, but the switching costs are so high that the word processing market is really a collection of monopolies. With a license like the WGL, on the other hand, not only would those switching costs be reduced, but the monopoly of one would crumble into a real market.
There are many ways one could expand on the idea, but those are just details. The essence is to gain the practical benefits and the higher ideals of free software without the revenue-destroying sharing clause. I don't expect I would actually use a license like this (for one thing I don't see myself being an independent software vendor), but it's possible. Nor do I expect that this would be anything but a temporary state of affairs; I see this as being more of a transitional mode before the rise of patronage.
Eventually, we are going to move to a patronage model. Rather than buying software/books/music/etc. per unit like they are widgets, the emphasis will shift to paying for something to exist, like a collaborative bounty. Freeloaders just aren't a problem with digital goods in that environment. That's the future. In a lot of ways, actually, that is the present, but filtered through inefficient, opaque mechanisms such as software licensing and market research. Current licensing models will eventually disappear. It will probably take decades to happen, and it won't ever achieve a complete victory. The WGL is just an intermediate stepping stone from the standard of today to that future. Each mechanism performs the same task of converting need, effort, and money into useful software, but each one does it better than the previous one. It is inevitable that the market will evolve to these better ways.