I think after all of the complaining about how WordPress is GPL and all themes and plugins that use the WordPress library is GPL, I think a solution would be to write a library that everyone can use GPL free. The library will have a clause, which will say that all commercial entities using the library will be required to pay me a sum of money in order to use the library in their projects. So actually, it will be dual-licensed, or tri-licensed. The first license will of course be the New BSD license, which basically gives everyone the right to use the Library with almost no exceptions for anything. That license will be for those using the project for free projects or for commercial projects that won't be distributed. The second license will be for distributed commercial projects, like premium themes and plugins that wish to have an End User Agreement prohibiting the user from redistributing the theme or plugin. The third will be LGPLv2 and up, if WordPress ever wanted to use the library and distribute it, but I doubt that possibility. However, it could apply to any GPLv2 or GPLv3 project.
I think part of the issue is that library is under the same license as the application WordPress. Therefore all code that links to it, has to also be compatible to GPL. This means that it doesn't restrict the user that isn't in the GPL. The clause to restrict Commercial entities shouldn't really apply since their license will not be GPL anyway. The licenses that work with GPL, namely the New-BSD and LGPL can be used without restriction. So if the project was GPL, then it would have to use one of the two, and it couldn't be the one with the commercial clause. It also means that the user will be able to take full advantage of the GPL, which means redistribution and selling it. If a commercial project wants to protects their rights, they'll use the library, or write their own.
Regardless, I think there are a lot of code in WordPress, which is done right and is almost impossible to reproduce without copying the code. Personally, I'm not going to rewrite the entire WordPress library. I'm just going to focus on the parts that Plugins and Themes use the most. I'm also going to focus on other components to experiment on how they could be improved for optimization.
Oh yeah, I'm also writing the library to where it will be fully unit tested, where applicable and with documentation. The progress is pretty slow with that, but it is worth it. It allows me to see in real time how far I need to go and how much I've accomplished.
The project is new, and right the repository is local to my machine. I'm going to put it up on the Google Code, when I get to the point where it can be reasonably be used in applications. Oh yeah, I'm writing the library for PHP 5.3, I'm going to backport it to PHP 5.2.x, but it won't be available on PHP4. Right now, there aren't any hosts that are using PHP5.3, because it hasn't been released. I want to see what it would look like using the top of the line PHP code.
I'm going to be posting more about the library. Well, I suppose I should have a disclaimer, I might not complete the library depending on what happens. It is going to be a lot of work, so I might not have the motivation to complete it. However, I'm going to spend as much time as I can get to it where it needs to be. At that point either someone else can take it on or I can work with some one on it.