In agent-oriented programming the antonym is depender, though in general usage the common term dependent is used instead. There is no common language equivalent for dependee', however – other metaphors are used instead, such as parent/child. The circumlocutions “A depends on B” and “B is depended on by A” are much more common in general use than “A is the depender, B is the ' dependee ”.

In the software industry we use "dependency" to refer to the relationship between two objects. We say "looking for dependents" for relationships to dependent things and "looking for dependencies" for relationships to prerequisite things, so it gets that connotation, but the literal meaning is the relationship itself, not the object. Finding a better word is exactly the point of the question

I don't think this is a good overload of 'subtraction'1Olivier Lacan@olivierlacan·Jan 14, 2019Yup. I don’t either.