What's the differences between open content and free content?
Free content, or free information, is any kind of functional work, artwork, or other creative content having no legal restriction relative to people's freedom to use, redistribute, improve, and share the content. Importantly, when free content is modified, expanded, or incorporated within another work, the resulting work must also be distributable as free content (see share-alike). To be considered free content, a work must allow modification and redistribution.
Free content licenses generally differ from open content licenses in that they require a "source" copy of the content to be provided. For example, a free content publisher should make the source document (e.g. InDesign or word-processor file) available along with a PDF, which in this case would be considered the "object" copy of the creative work. Some free content licenses have stronger requirements. For example, the GNU Free Documentation License not only requires that a "source" copy of the content is provided, but that the source copy should be in a "transparent" format, in other words, in an open format whose specification is freely available to everybody.
Quoted from Wikepedia
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