What programming language should I learn to develop accessibility software?

Depends on the platform you're building on. What kind of disability problems do you aim to solve?

You'll end up using different languages on web vs. a mobile app vs. robotic assistance, etc

Generally speaking, can't go wrong with learning python first. If you end up needing something else, you can figure it out later

Hi a screen reader for windows called NVDA is written in python.http://www.nvaccess.org/It's open sorse, if you wanted to look at some of the code you can. What about a11y soft wair intrests you? I am blind so i just know about screen readers but the a11y field is broad!

Accessibility is a property of a system's overall design. It is a higher level abstraction than a programming language or the function of the system.

What sort of systems are you interested in making more accessible?