They did perform the audit in collaboration with the author[0], so chances are it's fine, but you never know when a new manager might come in and flip the script for what's acceptable use of the api.
Google did vet Mimestream as a general-purpose email client before approving API access, and on the paperwork for that process "general purpose email client" was the app category that I selected, so I'm hoping all will be OK, or else I will be really scrambling to implement new protocols :P