I don't know whether you're trolling or simply naive but that's clearly fraud and the scenario you describe explicitly aims to commit fraud.
At the very least it's violating the terms of service. But very clearly the two of you would have conspired to defraud GitHub and in this case there would even be evidence in the form of an HN comment where you literally ask if this would work.
You may think you're clever but trust me when I tell you that no, you're not, and I've seen enough people try to be exceptionally clever and think "plausible deniability" would cover their butts and then get sued for fraud.
(A) two random developers that met each other at several conferences over the years, have contributed to a few same projects and really like the efforts the other one is putting into their OSS project
(B) two random developers that met each other at several conferences over the years, have contributed to a few same projects and want to fraud GitHub for the donation match
I think this could be a real practical problem for GitHub. And lawyering up against developers supporting the campaign potentially counteracts the marketing benefit of it.
If I was GitHub, I'd make a distinction between two random people shuffling 10 bucks back and forth and two people shoving hundreds or thousands around. The first scenario is probably an accident, the second is not. Come to think of it, they probably should have capped individual contribution matching to something reasonable (maybe they'll still do that).
Option (A) is the exact situation I'm envisioning.
Rather than waiting for some third party fans to give money, we'd be immediately rewarding the work that the other has done over the years with a one-off $5K (to maximize the match) contribution.
I'm not the other guy, but I honestly don't see an argument for why this is fraud. Is this against the terms? Can you point to a specific line in the terms forbidding this?
Your argument just seems like "this is clearly fraud and you can tell by looking at it"...