The word "free" in English, when used of material or immaterial goods, means "not costing or charging anything". In other words, that good can be used without having to pay money or anything else valuable. For example a free meal is a meal which you can eat without paying any money for it. A free service is a service which costs nothing.
If a software can be used without limits and without having to pay anything for it, what do you call that software? Free, of course. You don't have to pay anything to use it, so it's free. Plain and simple. If something is not free software, it means that you have to pay for it.
Now, the Free Software Foundation (FSF) went and gave their very own definition of "free software". According to them, it's not enough to be able to use the software freely without having to pay anything for it, but there are a bunch of additional rules in order for a software to be "free". These rules are so strict that they actually rule out over 99% of software which can be used at no monetary cost.
And that's not all: According to their definition, "free software" may actually cost money! Their definition and usage license allows someone to ask for money for the software, yet it can still be completely "free software" according to the FSF.
Ok, people can go and redefine the meanings of any words they like, of course. The problem with this specific case is that most FSF and GPL (their license) enthusiasts have jumped to this bandwagon of redefining the term "free", and actually have done it so fanatically that they ferociously defend the FSF's definition of "free software" over any other possible definition. They go and ferociously fight for anything not complying to the FSF's definition to not to be called "free software". They harass people on forums, they vandalize public wiki websites, they'll do anything to stop people from calling some software "free" if it doesn't comply strictly to the FSF definition. It's like a cult.
One sad victim of this war has been the POV-Ray raytracing software. The program can be used at no monetary cost whatsoever for any purpose (even commercial purposes), and even the source code is available for anyone to study and modify and distribute. However, the usage license of POV-Ray has one small detail which makes it "FSF-incompatible": It limits the usage of the source code directly in other programs (in other words, you can't take part of the source code and embed it in another program).
Because of this "incompatibility" with the FSF definition, GPL fanatics are fighting to the death in order to make people not to call POV-Ray "free". This fanatism even goes so far, that some GPL fanatics actively boycott and badmouth the program, for the sole reason that it's not "free" as defined by the FSF.
It's interesting that they show no such behaviour towards commercial rendering software which you can't use legally without paying money and is by all definitions not free. They only boycott and badmouth POV-Ray because it's popular, it costs no money, and doesn't fall into the FSF definition of "free". This kind of behaviour is completely irrational.
The FSF has hijacked the word "free" for themselves in relation to software, and they have got a large and rabid group of fanatics to back them up everywhere online. This is really insane behaviour.
Basic common sense says that you can't just go and redefine the meaning of a commonly used word and then attempt to impose that new meaning by force on people.
The motto of the FSF is that their definition of "free" means "free as in speech", not "free as in beer".
This is just ridiculous. The allusion is just wrong.
"Free speech" means that you are not limited to what the contents of your message are. In other words, you can express whatever you want (for example negative opinions of the government) with impunity.
"Free speech" does not mean "anyone is free to use the text in any way they like". Publications always fall into copyright, and even if they contain "free speech", the use of the text may still be limited. For example it may be illegal to copy the text and publish it in another publication.
Obviously this is not what the FSF means with "free", and thus the allusion is completely flawed.