Eric, how is your service tied to GitHub? As far as I understand it, you simply are a matchmaker for developers and advertisers. And you track clicks to the advertisers urls. Where the developers put the links to those urls is not your decision, right?
If so, I don't think GitHub has an angle to attack you.
A developer with a Commission Junction account could very well put CJ links in their README. That would not give GitHub a vector to attack CJ.