After 10 years of intermittent work, a developer has completed a full reverse-engineering of the 1998 Ultima Online demo server. The project disassembled approximately 5,000 functions from MSVC x86 and translated them into portable C99 code, comparing each function against the original binary.

The demo server, bundled with the "Second Age" expansion, contained actual production code from mid-1998 despite limiting gameplay to the island of Ocllo. The developer fixed stability issues and discovered the famous ecology system still present but dormant in the code. Recent advances in LLMs finally made completing this seemingly never-ending task possible.

The rebuilt server now supports clients from version 1.25.30 up to 5.0.9.1, with five different encryption mechanisms reverse-engineered. While the original demo was 32-bit, the new build targets 64-bit while preserving the original class hierarchy. The developer continues seeking original server files to improve the accuracy of this remarkable game preservation effort.