enable license :freemium

[rolandwalker]

This is styled as a PR, but intended for discussion.

Some of our previous license discussions have been too broad; it is hard to figure out four things at once. Let's approach one point here: is :freemium useful?

• does it cover many Casks?
• can it be clearly and objectively defined?

If yes, we can document it, as it already exists. If no, we should delete it from the code.

As a point of discussion, there is a lengthy Wikipedia page defining Freemium, which might be considered in favor or against. It does mean that the term is commonly used. On the other hand, we are not like Wikipedia. Their detailed breakdown of software distribution models is exactly the sort of tarpit we don't want to step into.

(Incidentally license :freemium is a special case in that we wouldn't need to do extra bookkeeping and define it into DSL 1.1. Because it already exists as an undocumented form, it won't break code that assumes DSL 1.0.)

Refs #6426, #7917, #7923, #5586
cc @Amorymeltzer, @vitorgalvao, @ndr-qef

[Amorymeltzer]

At the risk of overreaching, repeating myself, and sounding too broad, I think :freemium fits nicely into the license schema homebrew-cask has going for it. The primary purpose (as I understand it) of the license stanza is for searching, and to that end having clear and distinct categories is useful. Software is (largely) either :oss or :closed. Those high-level categories get broken down: for :oss that means how and under what terms "open" is defined; for :closed that basically means co$t.

On one end, :gratis is closed source, but free as in beer with no limit on use. On the other, :commercial serves a purely commercial purpose for the owner: closed source, the user must pay; there may be a limited trial period, but it must eventually end, leaving non-functioning software unless the user pays (hence, "trial" and "commercial").

There is a vast gulf in between those two extremes, where :closed can be used. :freemium, however, applies to most of that middle-ground, and aids in searching as it tells users "This is usable, ad infinitum, but you gotta pay for the good stuff." That's something I think most people would want. It allows more parallel structure among the categories, leaving :closed and :oss for higher-order usage and less-common cases within their respective subgroups. IMO this change would make the overwhelming majority of cases covered, and there wouldn't be a need for other more arcane models (more on this later) that would muddy the water.

tl;dr - :freemium is closed-source, always providing some functionality but with additional functions or services for a premium

[vitorgalvao]

I agree with including :freemium. @Amorymeltzer already made all the relevant points in favour. I worried about cases where there would be overlap, but :freemium is clearly defined as a subset of :closed, and you’re very right about these kinds of rules, @rolandwalker — even if our definition can be disputed on the outside, as long as we have a clear one on the inside, it’s a big win and will avoid us many discussions later and stepping on toes.

[rolandwalker]

That's good enough for me. @Amorymeltzer, I hope you don't mind if I cc you on the other remaining questions.

[Amorymeltzer]

It'd be a pleasure.