There is still much debate about the financial viability of releasing content under open source models. Opponents feel that it reduces the viability of an author/researcher to make a living from published work. Those in favour, argue that the author(s) will earn revenue from people who purchased the published work after reviewing the material (and of course, the increase in exposure by providing freely viewable/shareable material).
Here’s an important experiment in the value of open source content (a quick skim of the book reveals a high-quality, well-researched resource): Theory and Practice of Online Learning“…is concerned with assisting providers of online education with useful tools to carry out the teaching and learning transactions online. It presents, in an easily readable form, the theory, administration, tools, and methods of designing and delivering learning online.”