When SuperNZB is unregistered, it will download using two server connections. Once you buy a copy, it can use as many server connections as you have access to and will then download at maximum speed. For many people, such as those with fiber connections, two connections to the Usenet newsgroup server is plenty, and SuperNZB is truly free for them. For people who want to download in the background and not bog down their network, SuperNZB is also truly free.
All other features of SuperNZB work normally in “free mode” – the “check” feature to see if files are actually on the Usenet server, unRARing, unPARing, etc. Personally, this author normally runs SuperNZB with only 1 connection so that its traffic does not noticeably slow down his network.