The publishers should put the source code for the server into escrow under the condition that the code gets released with appropriate open source licensing if the company no longer runs any available servers.
Same issue with cheap IoT gizmos. Even if the retailers wanted to publish an implementation of their backend servers, they probably bought (rented) much of the functionality from a third party, under a license which forbids redistribution of the third party's IP.
Does anybody have some resources on running your own custom servers? For example, how private WoW servers work, were they reverse engineering?
[0] https://www.spgenerations.com/ [1] https://en.wikipedia.org/wiki/Survival_Project