Kaidan’s source code can be found at invent.kde.org.
Nightly builds for Windows are available as a standalone binary.
Kaidan is available as AppImage and Flatpak:
Alternatively, you can get the latest nightly builds from here.
Very experimental nightly builds (based on the KDE Frameworks master branch) are available. Please note that they are not signed with a proper key, and updating the app is only possible by re-installing it.