From iA wiki
GNUnet is an attempt to create an anonymous, encrypted, distributed, reputation-based network. A first service implemented on top of the networking layer allows censorship-resistant file sharing. The larger GNUnet goal is to provide an infrastructure for secure networking. All communication in GNUnet is authenticated and encrypted. The reputation model makes attacks on the network harder. GNUnet does not rely on any centralized services.
GNUnet is part of the GNU Project and licensed under the GNU General Public License (GPL). The developers page is reguarly updated. Thus far, GNUnet is not widely used, nor comparable in functionality to its contemporary peers. A recent (Dec 2002) update rendered all older clients entirely obsolete and incompatible, indicating the newness of this project.