Certainly within the UK I would argue with some force that themes indeed do form original works under the CPDA 1988.

Your first point in support of your claim is that:

‘Its contents are combined with the WordPress code in memory to be processed by PHP along with (and completely indistinguishable from) the rest of WordPress. ‘

This is true however, it is also true for almost all computer programs. As you will be aware, all programs make extensive calls to APIs and most rely heavily on the resistance of dlls and other such core operating system functionality. I think we can both agree that this is not enough to force the work to be categorised as a derivative work and I struggle to see how you can see WordPress themes as an exception to that general rule.

A more practical point that your raise is that:

‘The PHP code consists largely of calls to WordPress functions and sparse, minimal logic to control which WordPress functions are accessed and how many times they will be called.’.

This is true for the themes bundled with WordPress, but if you look at the themes developed by users you will hopefully see that the balance is completely different. If we take, for example, a company using WordPress as a CMS rather than a blog, then on most pages the limit of the WordPress calls will be ‘the loop’ with a substantial amount of extra code forming the basis of the website. If we are to say that by virtue of using the loop in the code that a theme will then be derivative then, following that logic, surely we must also say that any website that makes use of the jquery library is derivative of that?

I assume from your stance that plugins are viewed in the US as derivative works (as they rely far more heavily on the existence and functionality of the core ‘program’ (in this case WordPress) to function then themes do)? Within the UK that has repeatedly been found not to be the case. For us the rule is to look at the work as a whole (Ladbroke (Football) v William Hill (Football) [1964] 1 All ER 465) when examining whether it is derivative rather than pointing to single lines of similar text.

Certainly when looking as a whole at the default WordPress theme and then, for example, the custom theme that http://www.vancouverconventioncentre.com uses, it would be very difficult to claim that they are materially similar. Is the loop substantial? To me it is merely a fancy include function and, as such, my answer would be no.

I would welcome your views on how the points I have raised interface with US law and your opinion on the ability of your advice to translate to other jurisdictions.

I do want to clarify that I am a solid advocate of theme/plugin developers licensing their works under the GPL. I think it only fair, given the fact that their work and its success relies entirely on a system that is popular, in large part, because it is open source.

Though Mr. Vasile’s comment doesn’t leave things wide open, I still maintain that the last paragraph leaves the issue, at the very least, unclosed. If a theme could function independent of WordPress, one could rightly suppose that such a theme does not require the inheritance of the GPL from WordPress. Whether this is done by making the theme entirely HTML or by creating (even theoretically) a system upon which the theme could function independent of WordPress, this constitutes a work that is entirely separate, yet entirely compatible with, the WordPress templating system, and therefore independent of the WordPress license inheritance.

As I said, I wholly encourage people to adopt the GPL for their themes and plugins, but I also wholly support those who maintain they have no legal obligation to do so.

That seemed like the logic conclusion of that thought. Or a small amount of WordPress code that falls under fair use.

I’ve just seen some troubling comments elsewhere that suggested that last paragraph left it all wide open.

Sure, I can elaborate. I’m just writing off the top of my head here, but imagine using WordPress to serve a single static page. You would use a WordPress theme that does not contain any php but is simply HTML. The HTML would look a lot like data that just passes through the PHP process to the client and does not include any blog entries or sidebar functionality.

It’s a trivial case that turns WordPress into a very complicated version of cat, but that theme would probably be a separate work.