What is Proprietary?
Proprietary meaning (i) Proprietary software is owned by a company which restricts the ways in which it can be used. Users normally need to pay to use the software, cannot read or modify the source code, and cannot copy the software or re-sell it as part of their own product. Common examples include Microsoft Excel and Adobe Acrobat. Non-proprietary software is usually open source.
(ii) A proprietary file format is one that a company owns and controls. Data in this format may need proprietary software to be read reliably. Unlike an open format, the description of the format may be confidential or unpublished, and can be changed by the company at any time. Proprietary software usually reads and saves data in its own proprietary format. For example, different versions of Microsoft Excel use the proprietary XLS and XLSX formats.
reference: Open Data Handbook – Glossary