The site posts a screenshot of an official Apple URL for developer seeds with the reference to macOS 10.13.
What you see here is a (large part) of the CatalogURL for developer seeds. A secure (HTTPS) link (note the green “Apple Inc.”) so this is not some fake link. I can’t wait to get my hands dirty…
MacRumors determined the full URL as:
It's likely that Apple will unveil the next major update to macOS at WWDC which takes place June 5th-9th. Just yesterday, Apple announced that it will begin accept WWDC scholarship submissions starting March 27th.
Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates on what's coming in macOS 10.13!