“This Windows 98 computer can still use ICQ in 2026 — not because the original service still exists, but because modern infrastructure recreates the service the old client expects.”
Historical client, private service
ICQ 2000b is an original historical client. It does not connect to the original historical ICQ network. Instead, it speaks the historical OSCAR protocol to a modern private compatibility server. An Open OSCAR-compatible server, hosted in Docker, provides the server role; modern Linux clients such as Pidgin can communicate with the same environment.
This distinction matters. The client preserves an old interface and protocol expectation, while the infrastructure is contemporary and privately operated.
Windows 98↓OSCARCompatibility server
Docker-hosted↓Pidgin
Modern Linux
FOLLOW THE MESSAGE
This static diagram prepares a future interactive explanation. It will follow a message from ICQ 2000b through OSCAR to the compatibility server and on to Pidgin. For now, it demonstrates the essential idea: protocols and client/server roles can outlive the original online service when a compatible service is deliberately provided.
OSCAR is the historical protocol family expected by this client. A protocol is an agreed way for software to format and exchange information; compatibility layers translate or reproduce the expectations that allow different generations to meet.