Well, the market for gaming in China is still growing, but to actually get INTO China you have to fullfill a lot of regulations. Many games are forbidden and must not be made available.
Also they have laws that people are only allowed to play for a couple of hours each day, which is manageable in internet caffes and with DRM controlled games, but I don't see how GOG wants to do that. But ... games for chinese speaking people outside China ... that's a different story. For that there are no regulations. Chinese people living outside China have the same hard time to do business with China than everyone else. GOG is probably just exploring new options, since there's many chinese games we never heared of, mostly shovelware of course. And these people might be interested.