Although CivOne is not finished, preview versions are already available for testing. You can download them here.
Current version: 0.1.0pre-alpha1-r1151
Windows 32-bit: civone-0.1.0pre-alpha1-r1151-winx86.zip
Windows 64-bit: civone-0.1.0pre-alpha1-r1151-winx64.zip
Builds for Linux will be released soon.
Builds for macOS are not well-tested and considered unstable. They will therefore be released at a later time.
The source code of CivOne can be downloaded from GitHub.