What is proprietary desktop publishing software?

Proprietary software of any type is software that is licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while other uses, such as modification, further distribution, or reverse engineering are forbidden.

Desktop publishing software is used to create page layouts with text, graphics, photos and other visual elements.

So, proprietary desktop publishing software is software in which the user is given permission to use the software under certain conditions.