There is absolutely no obligation to even reply to mails. Otherwise you fall into the trap of having to explain everything to everybody and not doing your project.
The level of entitlement in the discussion astonishes me. Someone has done a lot of work and offered it for free along with a license that lets people modify it and redistribute it and that is not enough. Instead of being grateful for it, people are demanding that the giver also make the changes that these people need and take on the burden of maintaining them.
To all those people:
Why should he? Do it yourself or pay someone to do it. It need not be any more complicated than that.
