Which of the following is not open-source software?

Concept

Open-source software makes its source code available under a license that permits inspection, modification, and redistribution.

Software that is merely free to download is not necessarily open source; the governing source-code license is the deciding criterion.

Application

Internet Explorer was distributed by Microsoft under proprietary software terms, and its browser source code was not released as an open-source project.

Contrast

• Fedora Linux is a community operating system released under free and open-source licenses.

• OpenOffice is an office suite released by Apache under the Apache License.

• Apache HTTP Server is a web server released by Apache under the Apache License.

Result

Therefore, Internet Explorer is the software in the list that is not open source.