Applescripts are launched with the do command; in Applescript, by contrast, Hypertalk scripts are launched by (as I recall) the do script command. But there are fussy things that happen around the edges in order to cope with errors or in order to close programs after opening them and the like; people talk about HyperCard as easy to program, but "easy" is a relative word, as the nine year old and the ninety year old facing a flight of stairs would tell you. It's only easy when you are able to do it....

HyperCard can certainly open Applications and so forth, but it relies on Apple Events for most anything it wants to do outside of its own world of cards and stacks, and that means you need to be running System 7 and a version of HyperCard written for it; and to script the Finder requires System 7.5 or better.