Mikael is interested in a vulnerability scanner published under the GNU GPL. Which of the following is he likely referring to?

Mikael is likely referring to OpenVAS as the vulnerability scanner published under the GNU GPL. OpenVAS is an open-source vulnerability scanning tool that provides extensive capabilities for network vulnerability assessment. Its licensing under the GNU General Public License allows users to freely use, modify, and distribute the software, which aligns with the essence of open-source software.

Nikto, while also a well-known web server scanner, is not under the GNU GPL. Instead, it is released under a permissive license, allowing for broad use but lacking the specific freedoms associated with the GNU GPL. Therefore, while it is indeed a vulnerability scanner, it does not fit the criterion of being published under the GNU GPL that Mikael is interested in.