It just occurred to me that the copyright: tag type as a name prefix seems a bit odd, when you consider there are creative commons works on the site, as well as categories like events/holidays that cannot be 'copyrighted'

floraverse is a creative commons example

easter is a 'copyright' type

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tl;dr Do you all think the name of the 'copyright:' tag type should be changed to reflect the scope of its category more accurately?

I was thinking maybe 'franchise:' or something similar,

but holidays and celebrations aren't really a franchise

Just dropping words: group, subject, topic, class, association

While copyright may make no sense in some cases, I'd be surprised if there was any common English word that could cover everything without any exceptions.

No, it's good as it is, even though holidays have been shoved in there. Even in these cases, commercialism is alive and well. The popular image of Santa is connected to Coca Cola advertising.

As to the CC example:

Creative Commons is built on copyright. Creative Commons licenses couldn't be enforced without copyright. So the nature of Creative Commons is not a reason to change this prefix.

https://en.wikipedia.org/wiki/Creative_Commons

Creative Commons licenses do not replace copyright, but are based upon it. They replace individual negotiations for specific rights between copyright owner (licensor) and licensee, which are necessary under an "all rights reserved" copyright management, with a "some rights reserved" management employing standardized licenses for re-use cases where no commercial compensation is sought by the copyright owner. The result is an agile, low-overhead and low-cost copyright-management regime, profiting both copyright owners and licensees. Wikipedia uses one of these licenses.