It is not a realistic option for an author of accessible software to ignore JAWS. Obviously, open source software has no obligation to support accessibility, but that means that it'll be used less (this does not just affect visually impaired people, but also organizations and companies that have a need or obligation to keep their systems accessible; ADA compliance, for starters).

So, yes, open source programmers are perfectly within their rights to ignore that audience, and that audience is perfectly within its rights to not use open source software that doesn't meet their accessibility needs and to warn others and advocate against the use of such software.