The edge server is programmed for realtime edge environments and therefore to run within a private local network. It is missing the security and user access layer that you would expect from a cloud server and it has discovery services that only work within private local networks.
That said, if you get nodejs installed on a local linux machine, the server should execute.
That specific error looks like you need to cd into the vuforia-spatial-edge-server directory wherever you downloaded it. If you follow the instructions here: https://github.com/ptcrealitylab/vuforia-spatial-edge-server/#installation the file index.js should exist in the cloned vuforia-spatial-edge-server directory.