There are two main differences,

One difference is the authorization method for anonymous users. When an anonymous user visiting HelpWiki site, first the system will check if this user has been authorized or not, then determine if this user can see private post or not. So if your system is an Application Help System, it will check if this user already login as an admin level user in the separate application. If your system is a Knowledge Based System, it will check if this user request come from internal network.

Another difference is the read and edit rights. Application Help System only allow admin user log into the system, so only admin user can add or edit posts, there are no user groups or user roles to control read and edit rights of the posts. However, Knowledge Based System allow internal AD users log into the system as editor, so these users also can add or edit posts, there are some user groups and user roles implemented to control read and edit rights of the posts.