GameRanger supports many GameSpy games; see GameRanger - Supported Games for a full list.
One user examined the protocols and setup of GameSpy, detailing his notes here: http://aluigi.altervista.org/papers.htm#distrust
In the set of links includes a server emulator that should function for games like Battlefield 2.
OpenSpy is an open source clone to GameSpy servers
Very limited emulator, but it's the only one still under active development in 2020.