The extension doesn't seem to work for me when making an HTML5 game. When running the code, the game crashes right after the initial load.
The error seems to be in the GMLive script file. When looking at the console on a browser the error is "method : argument needs to be a function"
You can repro this by creating a new project and just importing the extension. Commenting out the code on GMLive makes the first room load without issues.