No they are from various free proxy sites found by searching Google and testing. By renew if you mean when are sources changed, if a source goes offline or stops updating their proxies they are switched for another source next ScrapeBox update. But if you mean how often are the proxies updated with fresh ones, then it depends on the source some update their proxies hourly and other sources daily.
You can add your own sources too, just Google for free proxies lists/sites and add the URL to ScrapeBox and it can harvest and test the proxies from there.