Unfortunately, the truth seems to be that most people don't actually read the licenses they release their work under. You can see that a lot in the world of CMS plugins and themes (where the 'can share the work as you like') aspect of the GPL seems completely foreign to 'paid' plugin/theme developers and even with text and image based content under the Creative Commons licenses, where a site creator will often freak out about a competitor using their content despite clearly saying its under a Creative Commons license that allows reuse.

It's like they copy the idea from stuff like Wikipedia and then only later realise the implications of it. But yeah, that's why you should read the license you're planning to use and make sure it matches your intent before using it.