>"I don't see why should I lose my right to do something just because I'm doing it as part of a group" (maxharris) //
Just taking this and doing an analysis ...
A) The initial premise is that: one should make reasonable allowances, eg of low cost, to accommodate those who might otherwise be excluded from society in some way due to accident, genetics, medical conditions and such.
B) The subsidiary premise is that: this allowance should be provided as a legal right to those who would otherwise be disproportionately excluded from society.
I don't think that argument holds water against this initial premise. A group has more resources. Making multimedia content accessible isn't required of individuals because it's proportionally excessive. In the same way a small store might not be expected to fit a wheelchair ramp but a supermarket would be expected to (indeed floor level access would probably be stipulated at the planning stage if it weren't already by the supermarket corp).
To put it a different way: if one child comes up to you and asks for food out of a genuine need, you've got a truck full of food. You're probably going to feel morally obligated to feed them. Now suppose a whole country comes to you and says they need food. With that same amount of food you're not going to feel morally obligated.
So, it seems there is some cut off at which the available resources compared to the size of the problem make a difference. I think that is enshrined in the ADA in USA and certainly is in the DDA in UK law.
The final element then in the OP is that (C) Harvard and MIT have the resources and so should also carry the obligation.
I think this is actually where I don't agree. That whilst as a whole they have the resources, for this project they do not. The allocated resources for this project mean that if the obligation were applied to make release of videos require captions and braille transcripts and such that the means available would not be sufficient to continue the project.
An analogue question might be: Does a chain of tiny convenience stores have an obligation to put in wheelchair ramps in some stores even though for the specific store it would be an excessive cost relative to their income.
tl;dr I think it comes down to compartmentalisation of the institutions.
[Perhaps maxharris you're right but just need to present your argument differently?]