Considering that the first GPL Lawsuit was filed September 20th of this year, there really isn't a legal precedent set in the law books, afaik. Most disputes have been handled directly by the Free Software Foundation.

In the MySQL v NuSphere lawsuit the GPL came close to be examined in court, but the case was ultimately settled out of court in 2002. In the infamous SCO Group v IBM Inc. lawsuit the GPL might in the end be subject of a court ruling, but, as the case is still ongoing and will be so for a while yet, interested parties will have to wait and see on the issue.

any HTML file which merely makes function calls to this code, and for that purpose includes it by reference shall be deemed a separate work for copyright law purposes.

I am writing a website maintenance system (called a “content management system” by some), or some other application which generates web pages from templates. What license should I use for those templates?

Templates are minor enough that it is not worth using copyleft to protect them. It is normally harmless to use copyleft on minor works, but templates are a special case, because they are combined with data provided by users of the application and the combination is distributed. So, we recommend that you license your templates under simple permissive terms.

Some templates make calls into Javascript functions. Since Javascript is often non-trivial, it is worth copylefting. Because the templates will be combined with user data, it's possible that template+user data+Javascript would be considered one work under copyright law. A line needs to be drawn between the Javascript (copylefted), and the user code (usually under incompatible terms).

A diagram of the above content

Here's an exception for Javascript code that does this:

As a special exception to GPL, any HTML file which merely makes function calls to this code, and for that purpose includes it by reference shall be deemed a separate work for copyright law purposes. In addition, the copyright holders of this code give you permission to combine this code with free software libraries that are released under the GNU LGPL. You may copy and distribute such a system following the terms of the GNU GPL for this code and the LGPL for the libraries. If you modify this code, you may extend this exception to your version of the code, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

If I have to write my new themes in PHP then I will, if that will make you see that the code has nothing to do with xoops. My themes aren't event based off of XOOPS default themes. I am not sure where anyone got the idea that code could not fall under a private license. It is an original work.