Why is this game not on GoG?

[xman1 10]

I am ready to buy it again as it is one of my favs, but I am not always on an internet connection.  I understand it was on GoG at one point in time but it is no longer.  I bought ArmA Gold on this site, but there is no ArmA 2.  Please fix this!  There is no reason for this old game not to exist on this site.

 

https://www.gog.com/en

 

-X