1) Burn the ships
By committing so strongly to an anti-VC ideology, they forced themselves to focus on profitability. They required themselves to make a sustainable company without the expectations that eventually someone would expand their runway. In the process, they created a very attractive investment opportunity for the trillions of dollars out there sitting on the sidelines looking for the next big thing.
2) Everything has a price
Don't consider this a strike against the github folks, I'm sure they are strong and ethical people, but everything has its price. $100 Million is a lot of money and I'm sure it left the founders with a lot of peace-of-mind that will allow them to focus on building an IPO worthy company.
They haven't done anything immoral and no one gets hurt, rather many people may greatly benefit from this move. They changed their mind like everyone in the world does in the face of smaller sums of money than this.
Good luck Github.