(1) The nameless model of reality I think is implied by "marginal cost of production is zero" simplifies away some essential aspects of reality (as explained by the late, great, RIP Manny Lehman model of "software evolution"). As the article points out, bug fixes and updates of the existing copy are necessary (to wit, IoT botnets), and in this model one never speaks about the continuing cost to maintaining the zeroth copy.
(2) The anticipated rejoinder to observation (1) is that, given the source, the end-users can do all maintenance, customization, and extension themselves. What we know about complexity (again, thanks, Manny) of any non-trivial application puts the lie to this.
(3) The anticipated rejoinder to observation (2) is existence proofs such as the Linux kernel. My reply to this rejoinder is that Linux is largely corporate-supported as a complement to the supporters products/services.