Hi Mike! Welcome to the community
This beta is available for anyone to use---simply copy the driver code in from my first post and follow the rest of the instructions to integrate it with your Hubitat setup.
I label things as beta when I haven't completed the feature set or when I haven't been able to test everything. In this case, what's there is tested and is reliably working (I use it for notifications at our office).
If you'd like to make any changes or add to the source, feel free to submit a PR to the GitHub file! Otherwise, enjoy using the Slack integration, and let me know if there's anything not covered in the first post in this thread.