Quasebarth: I actually don't understand this developer remark. To me it boils down to the point that they do not trust GOG.com as a distribution partner which sounds alarming and seems to be something that should urgently be changed by the management of GOG.com.
How does an activation on Steam actually be more convincing? Does Steam send out a notification to the developer account every time the game is purchased or even every time it is started and played? If so, well GOG.com could easily send out a copy of the receipt that I get when purchasing a game here to the developer as well for every purchase, couldn't they? This way they would be spammed to the end with mails, but at the same time they would quite easily know how much is sold.
Yeah, they only way their argument makes any sense at all is that their games on Steam have third-party DRM, namely their own, that requires activation on their own servers (not only Steam servers) to track it. Even for single-player.
All the other developers/publishers on Steam who don't have their own 3rd party DRM on top of the mere Steam activation have exactly the same problem that they are describing, ie. they have to trust on Valve's reports on how many games have been sold.
Pheace: This really doesn't seem specifically aimed at GOG. Clearly they've had bad experiences in the past with other retailers, and the simple fact is, that GOG doesn't have any live updating of what's happening. Steam on the other hand probably has "Real-Time" (Imagine that's what he tried to say instead of retail-time) information for the devs whenever they feel like checking up on it (I imagine they can simply log in to see it).
That way the devs can see day to day what's happening with their game, Sales, Achievements, Progress, Users playing, Money earned from Steam cards participation/Market, average time played, Store page Statistics, Forum statistics etc etc. Stuff like that I guess. I've seen it mentioned many times Steam has a ton of information and statistics available for the devs.
So GOG could offer them a real-time online report of how many people have a Stardock game on their GOG account (purchased), if they really feel they can only trust that kind of report, and not a quarterly report.
I have no idea how that is supposed to be any more convincing, but there you go.
And as every Steam user knows already, e.g. the "time played" reports of Steam are quite erratic.