In a Nutshell
The 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 MuPDF in a closed source, proprietary environment, OR wish to receive technical support from Artifex, you must 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.