=== So what are the obligations if I want to use ScummVM to release my commercial game? ===
You need to comply with the [https://github.com/scummvm/scummvm/blob/master/COPYING GPL v2 license] used by ScummVM. In a nutshell, this means that:
* You need to provide with your software a notice that the game executable (or part of it) is subject to the GPL v2 license together with the full text of the license.