It's parasitic because they're charging authors and readers. If publishing is a service to the author, then the author is paying to have their work seen, so it

It's parasitic because they're charging authors and readers. If publishing is a service to the author, then the author is paying to have their work seen, so it should be open access. If publishing is a service to the readers (as with book publishing), the author should get a share of each copy sold to a reader. Charging both parties is only a viable business model because there's no alternative—which is exactly what these linguists hope to fix.