Thank you for the tip. I did some additional research, and with the help of two plugins, EventCalendar’s category is safely hidden from view. I’m writing a lengthy letter on my solution that I’ll post on EventCalendar’s mailing list.
If someone wants me to post it here, I will do so on request (living in South Africa, where broadband is absurdly expensive, I’m used to conserving bandwidth) …
This matter is now resolved.