The github repo is here, but if you are just looking for CIM compliance, it was added in version 1.2.0 which has been on Splunkbase for a while. Also 1.2.1 was recently added which passed Splunk's automated AppInspect process. It's currently waiting on some manual inspection to be ok'd for Splunk Cloud installation.
According to the details for the App, it is on the "Future Roadmap", snippet from details below:
URL => Splunk DUO App Details
-Add CIM compatibility.