Based on the description, and like igorsk's kindlefix script, this does not remove DRM but instead allows DRMed MOBI ebooks registered with a Kindle PID to be read on that Kindle.
So this will primarily be useful for MOBI lending library ebooks, but will also work for OverDrive MOBI retail ebooks (e.g. some, but not all, MOBIs from Books on Board). It won't work for DRMed MOBIs sourced from mobipocket.com, which supplies most retailers, because they won't accept the Kindle PID.
I am not suggesting that the tool should do more, since the Digital Millennium Copyright Act
makes it a criminal offense in the US to produce or disseminate software to circumvent DRM.