Is it legally and/or eth­i­cally okay, to build a busi­ness based on a GPL licensed soft­ware? To those of you unfa­mil­iar with the not-so-uncomplicated details of open and com­mer­cial licens­ing, this ques­tion may sound like a ques­tion you’d ask a stu­dent of media law. But the­ory turns into vir­tual real­ity when we take a closer look a The­sis, a very pop­u­lar Word­Press theme.

Unlike most themes, The­sis isn’t avail­able for free. Christ Pear­son is sell­ing his tem­plate for $87 per per­sonal site, and so he’s been rack­ing up sales. Why do peo­ple pay for The­sis when there are so many free themes avail­able? This ques­tion is a lot eas­ier to answer: Chris thought about what pro cus­tomers want and started to offer a flex­i­ble, highly con­fig­urable theme which caters almost every need of pro­fes­sional pub­lish­ers and pro-bloggers. But even though his sales fig­ures are sky­rock­et­ing, Matt Mul­len­weg, founder and head of argues that The­sis vio­lates the GPL license — because GPL-software not only is freely avail­able (in source code), but the GPL (Gnu Pub­lic Licenses) also states that all prod­ucts built upon GPL soft­ware must also use the same license. In other words: It’s ille­gal to make money on the hard (and free) work of others.

Today invited Chris and Matt for a Skype dis­cus­sion which cov­ers some very impor­tant aspects of soft­ware licensing:

In my opin­ion, Matt is right but Chris is not the bad guy here. I def­i­nitely think that pro­gram­mers should be com­pen­sated for their work — after all, if Chris hadn’t sold The­sis but given it away freely, he prob­a­bly couldn’t put so many devel­op­ment resources into his flag­ship product.

The same prob­lem actu­ally applies to many pop­u­lar plu­g­ins I use on this blog: Ajax Edit Com­ments and Pret­tyLink are both avail­able as pro ver­sion. I hap­pily spend a cou­ple of dol­lars on plu­g­ins that offer great value. (When it comes to soft­ware, “great value” in most cases means that it’ll help you to save time and work, or in this case blog, more effi­ciently.) Yet still, the GPL license must not be vio­lated. After all, we all profit enor­mously from freely avail­able soft­ware. And even though I under­stand Chris’ posi­tion, he tends to exag­ger­ate: The­sis is a nice theme, but stat­ing that it was the one cru­cial fac­tor which made com­mer­cial web­mas­ters chose WP is just ridicu­lous: here in Europe, many com­pa­nies use Word­Press, but The­sis is widely unknown.

So how can we solve this con­flict? Can ven­dors of pro plu­g­ins / themes change their busi­ness model to offer­ing the soft­ware for free but offer paid sup­port? The pro­gram­mers of Pret­tyLink and Ajax Edit Com­ments chose a dif­fer­ent approach. In both cases, there’s free ver­sion (avail­able in the WP repos­i­tory) and a pro-version avail­able on the author’s web­site after pay­ment. Legally, this doesn’t count though: no plu­gin or theme is a stand-alone soft­ware: with­out moth­er­ship Word­Press, the code is use­less — that’s what “builds on GPL soft­ware” means. Seems like this dis­cus­sion will keep going on for a while. What’s your opin­ion on paid Word­Press themes and plugins?