The desktop app is for macOS, Windows and Linux. Its release builds are signed for macOS and Windows, and on Linux it is an unsigned AppImage, checked against its published checksum; none is signed or released yet. The emo command line and the MCP server cover the same three systems.
There is nothing to download yet. When the first builds are available, the download page lists the exact versions, system requirements and how to check that a build came from us. Until then, any download that claims to be Emolysis did not come from us.
Each build includes the engine and DuckDB, so you do not need to install a database separately. The installation docs describe how to install each one and check that it came from us.