You are right that nobody is being physically forced to make this change, but I think you vastly underestimate the power of propaganda and social pressure.
In today's hyper-socialized society there is not really much difference between "you are forced to make this change" and "make this change or else you will be socially outcast by all your peers".
Github is used by millions of developers all over the world. There is almost certainly at least one person in every western software company that regularly uses github. They have the power to broadcast messages into every software company in the western world, and right now this message is "make this change or you are racist".
In today's hyper-socialized society there is not really much difference between "you are forced to make this change" and "make this change or else you will be socially outcast by all your peers".
Github is used by millions of developers all over the world. There is almost certainly at least one person in every western software company that regularly uses github. They have the power to broadcast messages into every software company in the western world, and right now this message is "make this change or you are racist".