This plugin is free to download on your Jenkins instance, however, an Amazon AWS account is required. As of the time of this writing, the plugin is looking for new maintainers.

Is Jenkins cloud free?

Good answer, but I think what's missing here is the fact that Jenkins is self-hosted, thus it's NOT free (unless you get hold of servers for free, which is not a realistic expectation).

Are Jenkins plugins open source?

Jenkins is a free and open source automation server. It helps automate the parts of software development related to building, testing, and deploying, facilitating continuous integration and continuous delivery. It is a server-based system that runs in servlet containers such as Apache Tomcat.