Just to be clear: it seems that the same exact binaries distributed via a docker image or through standard distro packages managers are free for commercial use. The difference is that obtaining it from you directly costs money. This is a part of the business model that HN users would likely find distasteful. You're charging people who aren't technically competent enough to realize that other places offer the same exact binaries for free. Why even permit the side channels in the first place?
That's also an incorrect characterization. Those 3rd-party channels do not give you the power to customize Caddy the way our build infrastructure does. Try customizing Caddy with plugins through apt or DO images and let us know if you find a way to do that!