The focus of this post is RSS and knowledge, but he provides an interesting description of what you get with freedom of knowledge. ICTlogy :: The four kinds of freedom of free knowledge
Let me adapt the GNU project definition of the four kinds of freedom of free software:
The freedom to use the knowledge, for any purpose (freedom 0).
The freedom to study how the knowledge applies, and adapt it to your needs (freedom 1). Access to the source information is a precondition for this.
The freedom to redistribute knowledge so you can help your neighbor (freedom 2).
The freedom to improve the knowledge, and release your improvements to the public, so that the whole community benefits (freedom 3). Access to the source information is a precondition for this.
[again, via Feedster.]