The OpenGuides network is the set of guides that exist under the .openguides.org domain, or possibly those linked to from the OpenGuides site. It is possible to run the OpenGuides software and not be part of the OpenGuides network. It is possible to run other software and call yourself an Open Guide, but again this is not part of the network.
When thinking about setting up your OpenGuide, you will want to consider the benefits of being part of the network. A link from the main site will drive traffic, contributors and search engines to your content, making you busier and more relevant. You'll have a snazzy domain name. You might even have someone take all the hard work of systems administration away from you. It's probably a good idea to get in touch with existing Guide maintainers and software developers to discuss joining the network, to smooth the process of setting up the software and webserver, and to request a DNS record (domain name) for your Guide.