Yes in the sense that users pool resources for the network, but no in the sense that Napster relied on a centralized database of content - whereas Freenet is entirely decentralized.

Also Freenet is much more general, you could think of Napster like a shared hard drive, whereas Freenet is like a shared computer capable of running decentralized applications like group chat, social networks, search engines, etc.

I thought Gnutella was a bit more like Freenet than Napster, iirc only the bootstrap was centralized.