Download of YaCy 3.2.5 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The program lies within Internet & Network Tools, more precisely Network tools. We recommend checking the downloaded files with any free antivirus. This free software for Mac OS X was originally designed by Yacy.
From the developer:
YaCy is free software for your own search engine. Join a community of search engines or make your own search portal!
There are these three use cases you can choose from:
P2P Mode
Web Search by the people, for the people: decentralized, all users are equal, no central, no search request storage, shared index.
Your Search Portal
Your YaCy installation is independent from other peers. Define your own web index and starting your own web crawl.
You may want to check out more software for Mac, such as Covenant Eyes or Throttled Pro, which might be similar to YaCy.