Comment by tete
Please make it open source. Please create an API. Please, if you feel like you have to have your own client, build it, but don't ignore the reality of Linux gamers using a whole set of tools and one doesn't need to reinvent the wheel.
Especially for the older games you will get a lot more reach. You'd even reach beyond Linux (BSDs, etc.).
Please don't forget that a big chunk of your audience are nerds and that a lot of games run on engine re-implementations by nerds.
It's great that you make a client, but if you really want to offer something that would make people get games on GOG then do something that Steam does not offer, while probably being easier for you.
If that is too much to ask, please, at least do it in an unofficial capacity.