An AppArmor developer works on the AppArmor security module for the Linux kernel, which provides a framework for managing application permissions and enforcing security policies. Their responsibilities include developing new features, fixing bugs, and improving the software's performance. They also work on policy development tools and contribute to the creation of policy descriptions for various applications. They collaborate with other developers and security experts to ensure the software is robust and secure. They may also assist in user support, troubleshooting issues related to AppArmor, and documenting updates or changes to the software.