Project Vice City is being built for GTA V through FiveM, on a licensed private server used for development. There is no public server to join, no whitelist to apply to and no download to install.
The long-term intention is to follow the setting into GTA VI when a licensed, technically supported multiplayer platform makes that possible. That platform does not exist today. We are not assuming an API, a release date, or migration tooling, and we will not advertise a service we cannot operate.
The layout of the framework reflects that position: engine-specific behaviour is isolated behind a platform adapter, and portable rules stay free of engine calls, coordinates and models. That keeps a future transition a matter of adding an adapter rather than rewriting a community.