I figured out how to get around the unable to launch issue. Long story short, there's some issues using js to dynamically load files while running the file:/// protocol on modern browsers.
You can disable this safety feature on Chrome (using a launch flag) or on Firefox (using a setting). Just look up how to disable CORS on your browser of choice.
NOTE: This is a safety feature, and there for a reason. Don't load sites with it disabled, and only run trusted local files. Re-enable the feature when you're done with the game!
For a more long-term solution, the dev should take a look into bypassing this security feature. There are a few workaround, beyond just hosting your own local server, from what I read.