If this is a public repository, you would want to replace the GMLive script with a copy from the extension when you first download/check out the repository.

If this is a private repository, you can keep GMLive in the repository by removing the scripts ➜ GMLive ➜ .gitignore file using Explorer/Finder.

What happens here is that GameMaker does not have a formal way of using paid extensions in public/open-source projects (as they are in the project folder), so GMLive’s main script is omitted from the repository and a simple “fallback” script is created if the script is missing. That’s what the popup is, though there should also be a regular popup and a message in Output informing you what had just happened.