In a Nutshell
The Ghostscript and MuPDF AGPL license is for developers who wish to share their entire application source code with the open-source community as free software under the AGPL “copyleft” terms.
As soon as you want to distribute Ghostscript or MuPDF in a closed source, proprietary environment, you have to purchase an Artifex commercial license.
More information regarding licensing may be found on the Artifex licensing page. If you are uncertain as to whether you can use the AGPL release or require a commercial license, please contact us at Artifex Sales and we’ll be happy to help.