Lambda the Ultimate

TileStack is an attempt to resurrect HyperCard and bring it to the web.

Running online there are going to be limitations about which stacks can be ported, which may reduce the usefulness and impact of this project, but maybe a standalone version will come later.

The system compiles Speak (the TileStack version of HyperTalk) to Javascript. If the result is not obfuscated, something I haven't verified, it may be possible to augment the output from TileStack with additional capabilities not supported or not yet implemented.

From the compatibility angle it is interesting to note that they renamed the language and seem to imply they are going to extend it beyond HyperTalk, without giving any specific guarantee about future compatibility. I'd suggest releasing the compiler that's as close to full HyperTalk compatibility as a separate product (or even, if they can bring themselves to do it, releasing it as open source).