While the tool itself was a technical marvel for its time, downloading it today from unofficial websites is highly discouraged for the following reasons:

Version v1.3.9 introduced several notable updates over its predecessors. The main addition was – the ability to convert retail editions of Office 2016 (Word, Excel, Access, OneNote, Outlook, PowerPoint, Publisher) into volume-licensed versions that KMS activation could handle.

Understanding KMSAuto Net 2015 v1.3.9 by Ratiborus: Uses, Risks, and Legal Alternatives