5
Actually, under the GNU GPL you can charge for whatever you want, you just can't restrict what the person does with the code once they have it (unless they obtained it unlawfully of course, but good luck trying to chase that down). Most commercial software companies releasing under the GNU GPL (as XOOPS is released) don't actually charge for the software itself though, but rather for the time in producing it. Totally depends on if production is volunteer based, or if there are mouths to feed at the end of it.