You only want to use this if you have set your DNS up such that the ACME token should be created in the zone apex - for example, as described in this blog post.

The original source code can be found here.

The original README file can be found in README.orig.

This script assumes the zone will be empty when it starts, and empties the zone again when it's finished. Even if this causes it to fail occasionally, it is probably fine, just something to consider.