- The online roster lists 8,945 programming languages from the 18th century to the present.
- It includes 7,800 influence links and over 11,000 citations.
- The genealogical tree of HOPL is maintained by librarians Diarmuid J Pigott and Bruce M Axtens, with quartermaster Steve Poulson.
- The content is copyrighted by Diarmuid Pigott from 1995-2020, with a prohibition on copying or reproduction.
- Errata and crash notifications can be sent to hopl.acquisitions@gmail.com.