Open Age is a community-driven effort to rewrite the Age of Empires engine from the ground up as free, open source software. The project lives in the SFTtech GitHub repository and targets PC, aiming to let fans run and eventually expand on the classic real-time strategy experience without the original binaries.
The latest commit advances the codebase further along that goal. While the project is still in active development and not yet a full replacement for the original game, it represents a serious long-term preservation and reimplementation effort worth keeping on your radar if you care about the future of classic RTS titles.