[yawpitch]

Pretty sure that, legally speaking, an author publicly declaring that a piece of publicly published work is offered as open source, coupled in this case with also indicating (albeit indirectly and not obviously) via the Cargo.toml that the work is specifically licensed under “MIT OR Apache”, is more than sufficient to block them from ever successfully pursuing someone else for damages under their copyright for use consistent with those indicated licenses. That declaration effectively does make this “open source” under the plain meaning of that term — the source is openly available, and the author’s clear and openly stated intent is that it is offered as openly available under specific licensure terms — what it probably (or at least properly) is not is “Open Source” per the definition of the OSI.

The author should certainly clarify the license terms if they want this to be widely used, but though I wouldn’t use this for MANY reasons, not one of them is fear of having violated the author’s copyrights.