Free online games platform (juegos gratis), with an open source client. LGPL repo for Desura client. Potentially out of date. See https://github.com/desura/desura-app for newest (LGPL) client.
We had around 10 issues on our internal bug tracker with quirks that windows did with normal windows and the desura windows didnt follow like drag to top of screen to fully maximize.
Wich issues for example? I only noticed, that the windows looking very windows 7 like on a windows 8 machine, but nothing else.