Looking at the "forked from" field doesn't tell you whether a) it's a random forker who wanted to make a few changes, in which case you want the original, or b) the original project changed hands or was abandoned and the forked version is canonical, in which case you want the fork.
That's not the only problem.
Even with the network tree, you're still screwed, because Github's network graphs are incomplete. Take this brief conversation from ruby-talk last year:
http://www.ruby-forum.com/topic/203100
I challenge you to deduce the result of that discussion from the information available here:
https://github.com/rightscale/right_aws/network
Right now, without delving into the code, I still can't tell which one is supposed to be canonical, if they've diverged irreparably, or if it just doesn't matter which I pick.
That's not the only problem.
Even with the network tree, you're still screwed, because Github's network graphs are incomplete. Take this brief conversation from ruby-talk last year:
I challenge you to deduce the result of that discussion from the information available here: Right now, without delving into the code, I still can't tell which one is supposed to be canonical, if they've diverged irreparably, or if it just doesn't matter which I pick.