I only know from friends living there, take anything I say as speculations, but what I gather is that they see open source as a technical advantage over starting from scratch, it's not a spontaneous movement.
it makes sense from the point of view of a country that has gained a leading position worldwide from accurately reproducing something that already existed.
judging from the number of Linux distro they are releasing I think they are pretty serious about it.
Exactly. Reimplementing GitHub is not building a rival to GitHub. Like Wikipedia the value isn’t in the platform but the content hosted by the platform. Until there is a critical mass of open source software hosted Chinese GitHub provides very little value.
In the west we had a critical mass of open source software and then built GitHub. This is putting the cart before the horse.