If you're talking about a static HTML page, or even a JSP page, you can just add it to the extracted directory of the JForum web app and link to it. If you want that page served through JForum, and use a FreeMarker template you created, you need to do a number of additional steps: create the template (most easily by basing it on some other template like user_profile.htm), define the template in templatesMapping.properties, create an Action class that uses the template (possibly based on net.jforum.view.forum.UserAction, in particular its profile method), and define the URL of the page in urlPattern.properties.
As to the version, you should not make anything based on JForum 2.1 publicly available. And even if it's used behind a company firewall I would caution against it - it has publicly documented security holes. You can get the current version from https://sourceforge.net/projects/jforum2/files/, or -even better- grab the latest source code from SVN - it has a number of additional fixes and features.