Peter Suber, in the August 2008 SPARC Open Access Newsletter just released, has found an elegant solution to the emerging need for definitions to clarify the two basic concepts of open access, free as in free to read and free as in free for use. The distinction between gratis and libre mirrors a similar distinction in open source software. While the terms may be unfamiliar, this could be an advantage, as there would not be conflicts with preexisting uses of words.
This is an important, and useful, distinction. There is much discussion about gratis open access, as this is often the focus of open access policies.
Libre access, or freedom for use, is a very important concept. It is a reflection of the maturity of the open access movement that this distinction needed to be made, from my perspective. Now that we have 50 open access mandates with more coming, and a scholarly communications system well on the way to transition, it is time to be talking about libre access.
The Libre concept, to me, is very similar to what we librarians have been talking about for years even with subscription resources. Even when we pay, we may or may not be able to make certain uses of material, from printing and downloading to interlibrary loans. Creative commons licensed material is beginning to show up in our subscription resources; so far, this is likely only occasional, but this is the tip of the iceberg.