> It allows certain sections in a work to be unchangeable, such as the front-cover and back-cover texts, so that the information in the original publication won

> It allows certain sections in a work to be unchangeable, such as the front-cover and back-cover texts, so that the information in the original publication won't be distorted. That way, the author of the manual can receive credit. And also the author can insert whatever sponsorships, dedications, and website URLs in there. And this is key, there are a lot of scam websites that just <iframe> existing websites and put ads outside the iframe. CC-BY-SA is a weak copyleft– akin to LGPL while GFDL is akin to GPL.