Download this installer and run it.
If you're using Windows 8 or later the Windows SmartScreen Filter might complain that it doesn't recognize this file because only a few people have downloaded it, yet. To start the installer, click on "More info" and then on "Run anyway".
Update instructions: After you launch Knossos, it should ask you if you want to update. Just answer "yes" and wait for the process to finish.
Install the knossos deb package.
Update instructions: Update the fs2-knossos package with an AUR helper of your choice or build and install the package again.
Download this DMG file, open it and drag the Knossos icon on the Applications icon. Now Knossos should appear in your list of installed applications and can be run like any other installed program.
Update instructions: Repeat the installation instructions again. When a dialog asks you if you want to replace Knossos, click "yes".
Run the following:
pip install https://pxo.nottheeye.com/files/test/knossos/knossos-0.15.0.dev0+73b131a.tar.gz