Gratis or libre Open Access
Internationally there is a difference between “gratis” or “libre” Open Access. The difference is the choice of copyright. Copyright is concerned with the question who may do what with for example a scientific article. The 'who' in this question is the holder of copyright. In first instance this is an article's author, but he/she may also transfer copyright to someone else. The 'what' refers to the right to (commercially) utilize the article. That is the right to publish the article and to multiply (copy) it.
Gratis Open Access – read only
If copyright is transferred to a publisher, the publisher receives the right to publish the article. If the article is freely available for reading only, but may not be distributed further or re-used, this is called “gratis” Open Access.
Libre Open Access – distributing and re-using permitted
In the “libre” Open Access publishing variant, publications can not only be read but may be also re-used by others without legal restrictions. For example, text mining of scientific publications may take place if these publications are available in libre open access. Libre Open Access articles may be placed on any website, used for lectures, of may be included in so-called readers (also commercially). There is no need for authorization by the author of publisher. A proper reference to the author however must always be included. Libre Open Access articles are often published under so-called CC-BY license.