Instead of rebuilding it I think it would be better to run the original client through a C64 emulator, and run this emulator in the browser, with some sort of 'modem over websocket' tunnel.

It links to a github...

https://github.com/frandallfarmer/neohabitat-doc/blob/master...

which mentions MongoDB, causing me to discount the project altogether as a pipe dream by people who don't know what they are doing, but will manage to make something simple, then a larger buggy and unstable version. Eventually it will be abandoned. This is the story of most "collaborative" open source projects.