shmerl: No, I don't buy the non profitability argument. GOG didn't demonstrate such an issue. Humble Bundle is way smaller than Steam and smaller than GOG as well, yet they are profitable enough to support Linux, and not only that - even work on porting some games to Linux themselves.
According to GOG's reps, the problem was not profitability, but their inability (until now) to find a way to provide long term support. The problem which they never really explained in detail. And even that is an imaginary issue, since GOG's Linux users didn't even ask for long term support. Short term like HB does would do for now. Yet GOG doesn't want to provide what the customers want.
No matter how they put it, support for any company is an expense (and a very large one in good number of cases), even if its for a small minority of customers . Thing is, if they start to provide support for linux, customers will ALWAYS expect support. Can a company provide support for X product sold and later down road withdraw that support and still sell the product?. That's a relevant question.
"Yet GOG doesn't want to provide what the customers want." - thing is, the majority of customers use windows based products even though a small minority would welcome linux support.