This is about free software, not open source software.

The "free" in free software is about freedom, not getting stuff free-of-charge.

English has a serious problem with ambiguity around the word "free". In the closely related Scandinavian languages, there is a difference between "fri" (as in freedom) and "gratis" (as in free of charge). Unlike in English, the Latin borrowing "gratis" is the common everyday word for things that are free of charge. Free software is known as "fri programvare", whereas free-of-charge software (a.k.a. freeware) is "gratis programvare".

In German there are at least 3 words that describe these somewhat related concepts. The word "Frei" is mostly meant as in freedom but can also describe absence of something. The latter form is usually used in compound words like "kostenfrei" which means "free of charge" however, most of those words can also be compound with "los" like in "kostenlos" which means the same thing and is used more often in this case. We also use "gratis" but mostly if something is given complimentary in addition to something else. Something like "buy one get one free" for example. Then we also have "umsonst" which is actually not related but commonly used by people to mean the same thing as "kostenlos". However, it really means "for nothing" like in "ich habe vermutlich all das umsonst aufgeschrieben" or "i probably wrote all of this up for nothing". So the differentiation between getting something for free and something being free (as in freedom) is quite clear. However, there is no german word for freeware as far as i can tell and nobody i know says something like "Freie Software" instead of "free software" or "kostenlose software" instead of "freeware" but that might be caused by my circle and is more often used then i recognized :)