The gamut of opinions ranges from "all software is AI" to "only humanlike intelligence is AI."
However, there is a clear distinction between AI and non-AI software: It is declarative rather than procedural.
A procedural algorithm only follows rules implemented by the developer. A declarative algorithm is a goal: get from point A to point B. The rules are developed by the algorithm itself.
Another way to look at the distinction is that an AI algorithm has some ability to generalize problems whereas a procedural algorithm solves only the exact problem it was created to solve. AI algorithms may adapt, learn, generalize, or create novel solutions that surprise their developer.
In other words, AI has a broader competency than deterministic algorithms. If AI software is ever created that is competent across many unrelated domains, it can be said to be generally intelligent (AGI).