The root problem seems clearly (to me) that he is the only programmer maintaining a system whose original authors are no longer available. The life of a software system is very much in the minds of the people who are making it, and when they are gone, this is a kind of death.

This has nothing to do with length of variable names, although it is tempting to ascribe one's frustrations with a codebase to lack of skill on the part of the original programmers, rather than lack of access to their thinking.