I intend to keep the package more or less up to date with Microsoft's repository (https://github.com/microsoft/terminal) until Microsoft decides to release the binary packages on the Windows Store for use, at which point, I will likely remove the package from my server as it will be obsolete with a first-party release of the project.
You can download the certificate and project here: https://tonoxisisle.services/windows-10/Cascadia/
To grab the APPX certificate, choose "Additional Links" and then choose Publisher Cert. As with all third-party, non-Windows Store APPX packages, you will need to import the publisher certificate into the certificate store. After importing the certificate, you can install the application via choosing the "Get the App" button. (It appears to be regenerating the certificate each time I rebuild the app package, so I am unsure how that will work :/ )
Please enjoy! I love this developer community and am normally an Android person, but since I was also curious about the new Windows Terminal, and wanted to give back to the community that has given so much that I figured I may as well publish the build I have. I attest that I have made no changes to the source, and only to the AppX manifest, and am willing to upload the sources on my hard disk if requested for others to verify.
(To see the new UI, including the new tab and settings button, press CTRL+T. To have the terminal always show tabs, choose Settings and then change
EDIT: The AppX package SHOULD support x86 machines as well, as I had built the package with x86 and x64 binaries. It does not include the ARM64 binaries, though if requested, I suppose it wouldn't be too difficult to update the app package with the ARM64 binaries.