How to treat packages without an OSI-approved license?

Had a quick chat with @StefanKarpinski about [BonitoBook's](https://bonitobook.org/website/) dual license ([PolyForm](https://github.com/SimonDanisch/BonitoBook.jl/blob/main/LICENSE) + commercial) disqualifying it from General registry.
I get the reasoning behind it, but its kind of sad, that I cant use any of the nice registry features (search, discoverability, compatibility checks, versions) for a package, which I'm totally fine to distribute free of charge, since I only want to charge for heavy usage.
Some notes from our chat:
Registry already ships some non-OSS artifacts, so policy may be worth discussing.
Custom registry for one package creates worse UX than URL installation.

Some Solutions:
* Multiple official registries with prompt on first Pkg use where users select which to enable
* Maybe have an official permissive dual license which doesn't have restrictions for distribution by Pkg
* User prompt when installing packages with non-OSS licenses for first time

I guess some of these ideas are longer out in future, but I was wondering if there's also any short term solution to get BonitoBook easy to install and depend on.

Start by reading the issue discussion and the linked BonitoBook LICENSE, then review how the General registry and Pkg currently handle package licensing. A contribution is complete when the maintainers agree on a concrete policy or implementation path for non-OSI-licensed packages and its scope is documented.

Written by the indexing model from the issue text.