This is really cool.
Font management in macOS has radically improved over time; there are people who’ll throw a lot of shade at macOS Catalina, but for every niggle and complaint there are a bunch of neat, clever little fixes and features that don’t necessarily get the exposure and appreciation they deserve.
Licensing additional fonts that can be delivered through Font Book is both smart and creative. It’s also something that could be extensible – while font licensing isn’t what the vast bulk of people would automatically think of as a killer feature in an OS there are plenty of folks in the creative/design world who would richly appreciate, say, some kind of macOS Font Store. As someone who works primarily with those kinds of users, I’d be more than happy to see specific cuts of fonts that could be automatically purchased or licensed and that would just plain work with the OS. I mean, if you’ve ever spent an hour or two digging through the font folders on macOS doing forensic font-management then you’d appreciate, well, never having to do that again.