Why does this games require admin rights in order to run ?

That is a really good question. Shabby programming probably.

Yup without any official input from GOG, I guess this is our best guess on this matter.

Although not directly related it does remind me a little of a few Linux libraries sets, like SDL, and SVGAlib. Something curious as I remember about programming in SVGAlib was that you HAD to have root access when you started. The reasoning was you needed special privileges to access high level functions, namely changing the resolution on your computer (from text to graphics). Course programmed right, the first line in your code activates the needed privileges, then you lost root access immediately after removing the unsafe aspect of it.

This is different in a Windows system where everything starts graphically, so I am not sure why they need admin access. Maybe it's based more on older practices like Win95/98 where you were assumed to have access to everything all the time, which is 'shabby' as it goes.