I definitely agree about the linked Wikipedia article on modality. Literary theory is probably not a good way to talk about modality with programmers, but the idea of modality isn't just about linguistics and literature, and isn't as obscure as you think.
A better starting point for programmers and computer scientists would have been modal logic, which uses the modal operators of necessity and possibility.
For example, classical logic uses propositions. I can say "P" in classical logic. In modal logic, I can say "P", "Necessarily P", and "Possibly P", where logical necessity and possibility are modalities. See http://en.wikipedia.org/wiki/Modal_logic -- it's a pretty good overview and it links the logical and epistemological senses of modality.
A better starting point for programmers and computer scientists would have been modal logic, which uses the modal operators of necessity and possibility.
For example, classical logic uses propositions. I can say "P" in classical logic. In modal logic, I can say "P", "Necessarily P", and "Possibly P", where logical necessity and possibility are modalities. See http://en.wikipedia.org/wiki/Modal_logic -- it's a pretty good overview and it links the logical and epistemological senses of modality.