It's open to personal interpretation. There are certainly a number of varied factors that could be used, but to start out I figure letting the community up/down

It's open to personal interpretation. There are certainly a number of varied factors that could be used, but to start out I figure letting the community up/down vote will determine a prevailing consensus on what makes a repo "similar." As for me, my primary factor is: mutually exclusive usage. If I need to scrape some page and want to find a jQuery like parser for node I'll either use JSDom or Cheerio, but not both.