Hello Johnty,
Thanks very much for the interest in Hauptwerk.
In general, we do fully support Hauptwerk on macOS/OSX X 10.12.x Sierra, and we found no significant issues within Hauptwerk itself on that version, except that on Sierra the following apply:
1. (Which you've already done): Apple's Java for OS X (2015-001) needs to be installed before Hauptwerk's installer can run: https://support.apple.com/kb/dl1572?locale=en_GB
2. Unfortunately the recent macOS 10.12.2+ updates (which Apple released just before Christmas) have caused an issue whereby Hauptwerk's installer may sometimes crash after prompting you to enter your computer password. Addressing that properly is a matter of the highest possible priority for us, but at the moment we need to await a fix from the makers of the installer authoring software that we use for Hauptwerk. For now the work-around is simply to try re-launching the installer and trying again if has crashed. Usually it will work successfully after a small number of attempts, but if not then downloading the file again may help (since the issue appears to be related to macOS's check for the code signature, as a result of the file having been downloaded). It may take a little perseverance, but our experience is that it will always get past the login screen eventually, if you keep trying it (even without downloading it again). Our apologies for the issue.
Hence please just try re-launching the installer after it has disappeared, and it should eventually succeed.