Runtime Revolution is a multi-platform development tool based on the same paradigms as HyperCard.
Unlike HyperCard, Revolution is available on Windows, Linux and Mac OS X (native), and supports modern application conventions and technologies (Unicode, XML, faceless applications, CGIs, etc).
Revolution's language is Xtalk based, just like HyperCard. It uses an object-like, English syntax that looks a lot like pseudo code. Objects can communicate using a message path, allowing objects to catch or pass messages up the path.
Revolution can use a separate runtime to execute apps, or if you use Revolution Studio or higher, it can build standalone apps. Revolution stacks can execute right in the runtime environment, which itself is based on the Revolution stack paradigm. The Revolution IDE therefore can be extended easily, and there are both commercial GLX 2 and open sourced IDE replacements -MetaCard.
You can get Runtime Revolution from Mirye Software.