Why do private servers and server emulators exist, and are they legal?
They exist because online games stop working when their servers are switched off, and their legal position is genuinely uncertain rather than clearly settled either way.
What they are. Independently operated servers reproducing the behaviour of a game's official servers, allowing a client to connect and the game to be played after — or alongside — the official service.
Why they exist:
Preservation. When a publisher ends an online game, the game ceases to exist. Unlike a single-player title, there is no copy to keep. For games that existed for years and represented substantial communities, that is a total loss of a cultural artefact.
Playing older versions, before changes players disliked.
Communities continuing after a shutdown.
Modified rules, progression rates or content.
Regions or languages never officially served.
The legal position, in outline. Several distinct issues arise:
Server software. Reverse engineering to create interoperable software has some legal protection in the EU and UK under specific conditions, and the position varies by jurisdiction and by method. Where server code was leaked or copied rather than reimplemented, the position is far weaker.
Client software. Players generally need a copy of the game client, and distributing it is infringement.
Terms of service. Connecting to an unofficial server almost always breaches them, which is a contractual matter rather than a criminal one.
Circumventing technical protection measures engages separate legislation.
Trade marks, where servers use the game's name and branding.
What actually happens. Publishers respond very differently. Some send legal notices and pursue operators; some tolerate private servers for discontinued games; and some have released server software or added offline modes when shutting a game down — which is the outcome preservation advocates argue should be standard.
The campaign. Initiatives have argued that selling a game which is later rendered unplayable should carry an obligation to leave it in a functional state, and this has attracted regulatory and legislative attention in several jurisdictions.
For players: running or using one carries genuine legal risk, varying by jurisdiction and by publisher, and the fact that a game is discontinued does not remove copyright.