A peer-to-peer search engine. Your searches are local to your own instance + distributed to your peers running YaCy to search their content as well. You decide what your node indexes. Your node + everyone else's make up the global YaCy search engine.
YaCy will work without centralized DNS.
It will work without central servers.
It's unknown or not applicable as to how user accounts are handled. It's unknown or is not applicable if YaCy supports cryptocurrency monetization.