Put simply, I feel a lot of what the GPL has been used to force on companies is unethical, and anti open source.

The GPL has very strict rules about how it is used, and if a single person in a company uses a wrong compile switch (eg inclusion of library code) the GPL HAS been used to force companies to open source the products that they develop. This is as anti-open as you can get. Open source is about willingly contributing to the world use, and allowing others to do as they wish (hence OPEN). It is not about making your license into a crowbar to be used to force companies to give up there primary source of profit and release there secretes into the open source. Truly open source developers are happy for there code to be openly used (including in otherwise closed source projects), as that is the meaning of Open Source after all.

Having watched a few closed source commercial products be forced into the Open Source world, either because a developer made an error unknowingly getting some GPL code in the product, or because someone that was anti-commercial found there way in and intentionally snuck GPL source into the product (not proven, highly suspect), I can not support a crowbar license. This is my personal view of things, and I will not point at well known people that have used it as a crowbar in the Open Source community.

So I can not see a license that is designed and has been used to force companies to release there trade secretes as ethical. It is not ethical in any way shape or form. Read the terms of the GPL, and how strict it is about being forceful to release your code, even if it is do to a mistake by one developer that the company has zero knowledge of said mistake.

There are some that say they think that the reasons for the decline of the GPL are do to it being an "Ethically pure" license. In my view, as a result of it being used as it has, it is the furthest thing from an ethically pure license, it is a very unethical licnse in my personal view. I would guess that the decline is likely do to more and more people seeing the fact that the GPL can potentially be used as a prybar, as well as the fact that it has been used as a crowbar in a few cases known of already. As people see more of this it is likely the GPL will become less popular in my view.

There is nothing wrong with a license that requires that only the source that comes from Open Source be made available. That is to say a license that allows the project to remain Closed Source and only requires that the source tat comes from an Open Source project so licensed be released (even if the two are linked, the closed source should still be allowed).

The trouble is with licenses that require that any linked code be made open source as well as the originally Open Source code. It has been proven that some of the people high in the GNU foundation are more interested in forcing everything closed to be opened, and do not care about true Open Source. By what they are doing with the GPL and similar licenses is as strongly apposed to Freedom and Open Source as is possible.