Open-source Go server brings classic AIM and ICQ clients back online

An independent developer has released Open OSCAR Server, a self-hostable instant messaging server written in Go that accepts connections from classic AOL Instant Messenger and ICQ clients. The project, hosted on GitHub under the developer handle mk6i, gained visibility after surfacing on the front page of Hacker News.

A reimplementation of the OSCAR ecosystem

The name refers to OSCAR, the protocol family that AOL's messaging services were built on. According to the project's GitHub page, the server reimplements enough of that stack for vintage Windows AIM clients — versions 1.x through 7.x — to sign in and operate largely as they did when the service was live.

The supported AIM feature set goes well beyond basic messaging. The project lists away messages, buddy lists, buddy icons for clients v4.x and v5.x, user profiles, chat rooms with both public and private chat exchanges, per-user privacy controls to allow or block specific contacts, the era-defining warning feature, and user directory search. File sharing is partially supported: Direct Connect and Get File work on a LAN only, while Send File functions over both LAN and internet connections.

Compatibility extends beyond the official AOL clients. The server also speaks the TOC1 protocol used by Quick Buddy, gaim and TiK, and the TOC2 protocol used by vAIM, Miranda around v0.4.0.3 and iEM 1.0.1. A screenshot on the project page shows Pidgin connected successfully.

ICQ clients supported too

On the ICQ side, the project supports Windows ICQ clients from the 98x and 99x era through the 2000x, 2001x, 2002x and 2003x releases, plus versions 4 and 5. Supported functionality includes instant messaging, profiles, user search, presence statuses and offline messaging — the last of which matters for a server that may not have a large pool of simultaneously connected users.

Deployment and administration

The project provides quickstart guides for Linux on x86_64, macOS on both Intel and Apple Silicon, and Windows 10/11 on x86_64, along with separate setup guides for installing AIM and ICQ clients.

Administration is handled through a Management API, documented with an OpenAPI specification, exposed on port 8080. Endpoints cover the full account lifecycle — listing, creating and deleting users, and changing passwords — as well as listing active sessions for logged-in users and creating or listing public chat rooms. The documentation includes worked examples for both Windows PowerShell and curl on macOS, Linux and FreeBSD. ICQ accounts are created with numeric screen names in the same style the original service used.

An explicitly independent project

The GitHub page carries a disclaimer stating that the project is an independent, open-source initiative that is not affiliated with, endorsed by or associated with AOL or Yahoo! Inc., and that it is entirely non-commercial, generating no revenue and accepting no donations. The code is released under the MIT license. Development is described as active, with contributions welcomed and a Discord server available for help and community discussion.

Why it matters

AOL retired AIM in 2017 and ICQ was shut down in 2024, leaving decades' worth of clients as orphaned software. Open OSCAR Server demonstrates that those clients were never the whole story: because the protocols of that era were sufficiently observable and documented, a single developer can rebuild a working server and turn abandoned applications into living software again.

The project sits at the intersection of several current interests — software preservation, self-hosting and retro computing — and offers practical value beyond nostalgia. Communities that miss the semantics of old-school messaging (chat rooms, away messages, granular presence statuses) can now stand up their own instance rather than waiting for a modern platform to replicate them. The MIT license and stated openness to contributions mean the work can be forked and extended even if the original author moves on, and for anyone studying protocol design or reverse engineering, a working Go implementation of OSCAR is a useful reference artifact.