[thewebguyd]

People did it for World of Warcraft, and continue to do so with each expansion.

I can host and play a WotLK server locally, offline on my desktop with AI player bots with minimal issues thanks to the work of the community

[account42]

WoW is slightly more popular than the average abandoned game. These kind of reverse engineering efforts (re-implementation really without access to the original server) are possible but require huge efforts and thus rarely happen.