Ever hear of WordPress app themes? They're somewhat new. These are no ordinary themes. Take for instance a dental office. You walk in and the dental assistant makes an appointment on the scheduling app. Only it's not an app per sé, but a WordPress theme that acts like a full-blown web application. The application may use some features of WordPress, but may not use others. Some of the files will load via an MVC framework kicked off by WordPress calling a theme's index.php file. Some of the files may use WP API calls, while other files may not use a single WP API call at all. Some app themes may simply use WordPress as the sales mechanism because things attached to WordPress have market uptake. (Note, almost all app themes are not available on wordpress.org.) Some app themes may simply use WordPress to borrow the same database, provide easy admin panels that people are used to using, and the rest might be something else entirely. Some may use pages and posts inside the app theme. It depends.<p>Now that you know what a WordPress app theme is, the question is, "If a given PHP file doesn't make a single WP API call in it, but the parent file that called it may make a WP API call, does that file also mean it must be GPL as well because WP is GPL?"<p>Here's what the FSF told Matt Mullenweg about it:<p>http://wordpress.org/news/2009/07/themes-are-gpl-too/<p>However, did the FSF take into consideration my question above in the case of an app theme? That's a bit different, don't you think?<p>Here's my conundrum. I've put family life on hold, which hasn't been easy for me at all for me and my marriage. I've been drinking water and eating bread some days, almost. I did all this so that I could have the time to spend 30 days coding a WordPress app theme. Now that it's finished, I want to market it behind a paywall and get paid for my hard work. I want to ensure that when I told my wife, "We'll make some great sales here on this," that I was telling something realistic. But there's woothemes.com and cheapwoothemes.com as an example. Like that, I don't want someone to fork my stuff and sell it as their own accomplishment, perhaps doing nothing but changing branding, eroding all my seriously hard work.
I'm not convinced WordPress themes are derivative works of WordPress, which is what you need to believe to make the GPL stick when you're not distributing WP itself.<p>But it really doesn't matter. Release your "app theme" under the GPL and don't worry about it. You're already meeting its requirements -- you have to give the source (the theme) to each person that purchases it. You're not required to give it to anyone else.<p>You're not required to license your other assets -- images, stylesheets, javascripts -- under the same license. So even though your customers can redistribute the PHP code, it's pretty worthless.<p>Still, I would put that all under the GPL anyway. It's not going to lose you a single person that would've otherwise bought your theme. WooThemes makes millions a year selling premium WP themes -- they're all GPL licensed.<p>I used to sell a WordPress plugin and theme set. It was pirated all over the place, on all the file sharing sites and black hat forums. If someone wanted it for free, they could get it. Didn't matter. Still made a quarter million dollars from people that wanted the latest version, from a trustworthy site, with support.
I think this is weird. Lets say, Wordpress is a commercial product. You won't even think a minute, that you didn't have to pay for it, even if you just use one feature. The same goes for the GPL.<p>And if I understand those "app theme" correctly, they use the backend of Wordpress. For storing data, for administration of the data, users, rights.<p>So I think the FSF is right. But the GPL doesn't say, you can't sell your themes, it just says you can't deny other to do, what you did. That is all.
In your case, to comply with the GPL you must give the sources to those who paid you for your theme. You also cannot stop your costumers from giving those sources away for free if they want.<p>You are not <i>forced to spread</i> the sources around, to publish them on github or similar things. That would be nice but is not needed.
Not a problem really.<p>People need security fixes. If they download from elsewhere, they won't get priority notification.<p>You can also obfuscate your code.<p>In the long run, you can also remove dependencies on WP, by writing your own code to access the database et c.