Where does this word "liberal" come from and what does it mean?  I'll dare a naive etymology to start:  "liber" is from "liberty" but I also see "book". 

Now checking Google...  Yes "tree bark" is a part of it, as if "liber" were some kind of papyrus.  The liberty one achieves by reading. 

These connect:  liberal arts; open minded;  catholic.

In the software world we sometimes pretend we have only the word "Free" which comes encumbered with two meanings: 

• at no cost ("the best things in life are free"); but also
• accessible and, more to the point, adaptable. 

We say "free as in free beer" to mean "at no cost" to distinguish that meaning from "free software" as in Office Libre.  "Free Software" is the other "free", as in "accessible / adaptable" -- it doesn't necessarily mean without cost.

But as R0ml points out (that's his nick, a handle, the "0" a zero):  we do have another English word that means freedom, which is "liberty".

"Liberal" in this sense therefore means "open to new uses", which gives a special spin to "Liberal Arts" and what that means. 

Richard Stallman, champion of Free Software and founder of the GNU project, explains that free software is the software we're free to change, to fix, and to share with others.

Historically though (leaving etymology behind for the moment), there's a lot more to be said about "Liberal". 

I tend to anchor our current concept of Liberalism not so much in the French Enlightenment, nor in the rise of the scientific method since Francis Bacon, but in early 1900s Vienna and the civilizational struggles that converged there.  I meditate on and study: the Vienna Circle, the rise of psychoanalysis, the two World Wars.

A pivotal figure in the Vienna Circle was Ludwig Wittgenstein, from a wealthy Viennese family.  He turned his back on great monetary riches to pursue a somewhat simple and monastic lifestyle, as a philosopher and as a friend and colleague of Bertrand Russell's. 

He was curiously misunderstood at first (including by Russell), as saying language without a strictly literal interpretation is verging on nonsense, whereas what he was really showing as nonsensical is our attempt to make strict sense of the ineffable.  There's a difference, albeit a subtle one.  His emphasis on Silence becomes a link to Quakerism.

A liberty one achieves through reading is the freedom to "misread" (Harold Bloom), by which I mean "to repurpose" or "spin" in ways unintended by the original author -- but then meaning is always greater than any one person intends.  Ownership belongs to the Zeitgeist.

Or call it the Ouija Board Effect:  a whole greater than the sum.  It always feels like "everyone else" is pulling on the Ouija thingy, called a planchette.  The psychologists have a simple explanation:  there's more of them than there are of you.  So it feels to each individual that new meaning "emerges" -- and so it does.

Fast forward to literary (liberal) America and to Norman O. Brown.  His book Love's Body made a big impression on me.  Its thesis:  the Holy Spirit is most alive when not channeled to mean one thing literally. 

Keeping meaning multiplicitious was more the Liberal way.  To clamp down, to get strict about it, to insist on the one literal meaning of it all, is to stress what's not free.  Freedom is in continuing revelation, remaining open to future meanings.