YaCy is a free distributed search engine, built on principles of peer-to-peer (P2P) networks "wikipedia YaCy".
After installation, you can use it to search the WWW, but not your own computer.
However, I have found a guide that shows how to configure it for the LAN ("set up YaCy on LAN without public network").
So I hope it might be configurable so it can be used for both.
Maybe you have a idear? I would like to use it in Linux Lubuntu.