My career prior to WordPress involved implementing regulatory documents into code. Tax regulations, employment regulations, etc. One thing I learned, early on, is that while code can't be ambiguous, legal documents often are. I used to spend an awful lot of time seeking clarification. With the GPL, because of vested interests, there's no easy way to receive clarification so instead you have to make up your own interpretation - but it's an ambiguous and unclear document when applied to non-compiled code. Different lawyers will give different opinions, but they are really just that - and the quality of that opinion will vary according to the time those lawyers have.

I know that a large client who is implementing WP was worried about whether it allowed others to 'steal' their copyright work - for example, if the code was leaked (accidentally or otherwise) could somebody, in effect, legally reproduce their site's functionality and design. The answer is a straightforward NO. In essence, the GPL does not force you into rescinding your copyright, nor is it anything like as infectious as people think.