One of the useful new security features in OS X Mountain Lion is Gatekeeper. By default, Gatekeeper prevents an application downloaded from the internet from running, unless the app came from the Mac App Store or from a developer registered with Apple. In both cases, the app's code has been digitally signed by its creator, allowing Gatekeeper to detect if the app has been modified by a bad guy. The signature also identifies the source of the app to Apple if it turns out to do something bad to people's Macs — Apple can then throw a switch and shut down the app worldwide.
Riveal 10.5.1 and Revelator 7.1.3 are digitally signed for Mountain Lion. On earlier versions of OS X, the signature is ignored. The Windows versions of the apps are not code-signed. Both apps now also require a Java SE 6 (or later) runtime — that means at least Mac OS X 10.5 (Leopard) and Windows XP.
By the way, if you want to run an app on Mountain Lion that hasn't been code-signed, there is no need to turn Gatekeeper off in System Preferences. Leave Gatekeeper turned on and instead right-click or control-click on the app, choose Open, and confirm that you really want to run the app. You only have to do this once to say that you trust this app forevermore, and Gatekeeper will still be there to protect you from rogue apps in the future.
The new version of Riveal also has improved for fans of Cyan's early game Cosmic Osmo and the Worlds Beyond the Mackerel. For technical reasons, sounds longer than a few seconds — mostly music — were broken into many short segments within the game. Riveal now combines them into complete songs. In addition, many more pictures can now be extracted from the Windows version of Cosmic Osmo.