An account is required so that you can keep your own unique records for each query sent, and the agents you are interested in. If you do not have an account, there is no way to segregate your records from those of others.
QueryTracker is free because it is our goal to collect as much data as possible about query letter results. To do that, we need as many members as possible to submit their data, and the best way to do that is to make it free.
So please, join us in building the web's largest collection of query data.