The section on integrating with a CMS is really interesting. Does the license require that you link to only a GPL-licensed CMS?

These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

I have never seen someone using this feature so I'm interested in examples as well.

I guess most people simply use Limesurvey as a stand alone application or run it at an iFrame inside their CMS.