What did Richard Stallman mean when he stated GNU was a free operating system?

In the free software world, there are several uses of the word "free." The two main ones are "free as in speech" and "free as in beer." Free as in speech means you are relatively unfettered in what you can do with the software. You can modify it, use it for whatever you want, and give it to others (or even sell it). Free as in beer means that you can obtain it for no monetary cost.

Richard Stallman originally envisioned GNU to be free as in speech. At the time he started the project (in 1983), internet access was slow and expensive, high-capacity storage devices weren't readily available, and very few people had a personal computer. It would have been infeasible to offer GNU on a gratis basis. Stallman actually used to charge $150 for a tape with the GNU software on it, plus $15 for a manual.