Apple's Sierra Public Beta program allows registered participants to download and install the latest developer builds of macOS 10.12 before its ultimate final release in the Fall. If the public beta program works like it has in previous years, developers will receive updates first and then a week or so later the public beta testers will get a version.
As a registered Apple developer, I've had access to macOS 10.12 since WWDC in June. As far as I've been able to tell, any scripts or apps from this site that are already downloaded on a machine that is updated to macOS 10.12 should work fine. But Apple has introduced new security features in macOS 10.12 that may affect some scripts or apps if they are newly downloaded to a Sierra beta machine (they won't behave badly, they just won't be able to be launched). Therefore: unless a script or app is specifically described as supporting macOS 10.12, don't assume it will work on Sierra. To be clear, there aren't that many downloads that will be affected and I'm updating those as promptly as I can.