I am not in any way GOG staff but part of the answer is simply that GOG is doing very well and has been profitable from the beginning. They keep saying this on almost every interview and every conference.

How much profitable? Well, come on. That must be partly a business secret. Even as a community we do not have a right to know all financial details. Does Gabe Newell tell Steam's yearly earnings to the world? No - it's a private information. Do major game companies publish game sales figures for each of their games? No, only when they see fit, when they can use it as advertisment and never exact numbers, because then competitors gain knowledge and this would be an advantage in the competition.

However, a little searching in the Internet about GOG.com would have brought you the information that they together with CDP are part of the Optimus S.A. company which is publicly traded on the stock market in Warsaw/Poland. As you know, such companies must fullfill higher standards of openness about their financial development as private companies. So, like EA, Activision, Take 2 but unlike Steamworks which is private, they publish quarterly and yearly reports. Being a polish company traded on the polish stock market, these reports are in polish, but google translate can help you translating them from their website which is easy to find. Keep checking these reports for information about future development. Finally, looking at the stock price development and market capitalization you see that GOG+CDP is worth millions, much less than one of the big publishers, but already not small-sized anymore and gaining momentum.

There you would see that GOG+CDP makes profit and is growing but has had huge investments in the last year (due to development of TW2). These investments now must prove profitable to facilitate further growth. Also a risk of the business model of GOG might be a lack of new games (with the announced new publishers I would think this is unlikely) or increased piracy on GOG games or legal problems (you never know about these things). On the other side, the business model of GOG scales very favorably with number of customers, meaning when number of sales increase by 163%, the profit will surely increase by a larger factor (you know: fixed costs versus turnover related costs, which are quite low here).

So, as a potential investor and community member you can get the normal amount of information to decide whether to invest or not in GOG+CDP. Maybe they will decide to publish more numbers, but I guess they won't - after all the competitors aren't too.