@on-line is a synonym XRI for @free. Technically speaking, they share the same I-Number and therefore the same authority. This means that all their settings, services and community I-Names are the same.
Since you can register free community I-Names under the @free root namespace at our site, this means in particular that all XRIs starting with @free are also resolvable by replacing @free with @on-line.
The following I-Names are automatically equivalent, without the need for any specific configuration.
Consider this a possibility for you to experiment with synonyms!
See our documentation for more information on this topic.