@mholt is being exceedingly generous to the whingers on this thread, on top of the generosity he's shown in writing Caddy to start with.
It's not 2005 any more, Sun Microsystems is long gone. You won't raise any money from a business model that gives away your best work or selling support contracts alone.
Caddy is a real innovation, and brings web server defaults bang up to date - it makes loads of complex configuration easy. It's already distributed in the finest tradition of free software - a liberal source code license with no restrictions. You can do what you want with it.
Like GNU in the 80s and OpenBSD in the 90s, Matt is selling the most convenient package and yeah - if that's the one you used and relied on for your infrastructure, you've got to pay, and not very much.
Matt has clearly worked hard at making that payment support as much as possible in terms of convenient corporate deployment. I really hope that works out well, and am glad it's a business model that supports Free software without any compromises.
What I think is interesting, is the licensing model is basically reverse whaling
The bigger the company is, the more likely they are to go with just building Caddy themselves instead of paying for it. So, the only people who need to run the commercial binaries are the situations where the licensing costs actually matter.
Maybe I'm underestimating the size of the demographic they're targeting, but it seems to me that the only market for Caddy is a fairly small niche of people who are unwilling/unable to run NGINX or set up their own build process.
The company that goes and builds this themselves instead of paying a small fee for it, would be a pretty stupid company haha...
There is a fork without the adware now, so the smart company will use the fork to get rid of the stupid ads.