Free as in lunch also exists in anglo culture, with the notable example of There ain't no such thing as a free lunch (TANSTAAFL). The concept of free beer sounds natural because there are multiple contexts where you could potentially expect beer to suddenly become free for whatever reason (someone pays for a round, festivals, college dorms etc.) Free pizza would be a good substitute as well. Some consumables just have associations that aren't completely easy to explain to someone not familiar with them.

From the Wiki article

> Richard Stallman summarised the difference in a slogan: "Think free as in free speech, not free beer."

Free as in lunch would also work, but I'd hazard to guess that "free beer" is more relatable for the target audience Stallman was addressing. That being - computer enthusiasts ("nerds") who skew(ed) largely male, 16 - 35 (roughly).

It’s common at western weddings and other lavish parties for beer and other drinks to be served to the guests for free. Hence, “free beer.” When people say to one another “hey, come to the party, they’ve got free beer!” It’s instantly understood that the beer is gratis, not libre.

The german Wikipedia has an article on free beer ("Freibier") if you do not mind a foreign language source.

Here is an excerpt with an example:

"Eines der wahrscheinlich größten Freibierfeste ist jedes Jahr das Sommerfest der Braustudenten an der Technischen Universität München am Standort Weihenstephan in Freising. Dort werden jedes Jahr über 150 Hektoliter Freibier von über 300 Brauereien ausgeschenkt."

Translation: "One of the most likely largest free beer fests in the world is the annual summer fest of brewer students at the Technical University of Munich at the location of Weihenstephan in Freising. Every year, more than 150 hectoliter [i.e. 15000 liters] of free beer from over 300 breweries is served."

Source: https://de.wikipedia.org/wiki/Freibier

It’s not as complex as you’re choosing to make it. When someone tells you, “There’s free beer at Oktoberfest,” is your first thought that the beer has no monetary cost, or that the beer is unencumbered by particular legal restrictions?

Now someone tells you, “There’s free speech at Oktoberfest.” Is your first thought that there’s no monetary cost to expression, or that the expression is unencumbered by particular legal restrictions?

(Happily, Oktoberfest has both.)

>I'm just wondering in what context or culture beer is considered free (gratis).

When beer is described as “free,” it’s understood to be gratis. When speech is described as free, it’s understood to be libre. These are used as examples for more ambiguous situations, since software can be one, the other, both, or neither.

>Why not say "free as in beer, not free as in lunch"?

For three reasons:

1. “Free for lunch” is a way more common phrase, and it already means “unencumbered by schedule or previous commitments.” 2. “Free lunch” is already part of a more common phrase which states that a free lunch cannot exist, ruining the effectiveness. 3. Beer and lunch are both expected to be gratis, not libre. Exceptions (http://freebeer.org/) have to explain themselves over that hill.

You are overthinking it here. It is not a carefully thought out phrase, but something Stallman came up with in a speech for a particular audience once, and it stuck.

Worth noting: beer is encumbered by legal restrictions in many parts of the world. In these places, even free beer is still not legally available to anyone under 16, 18, 21, etc...