Huh? The reason for attacking github seems completely obvious, given that the attacked projects were (1) a mirror of the nytimes Chinese edition (explicitly intended to counter Chinese government censorship), and (2) anti-great-firewall-of-China tools...

[Not that they hoped to actually keep github down in the long run, but rather were probably trying to send a message that "hosting info the Chinese government doesn't like will make your life annoying so better not do it"...]