LiveCode can import HyperCard stacks. You'll need to use LiveCode version 6, since the HyperCard import functionality has been broken in LiveCode 7 onwards, but you can import a HyperCard stack using LiveCode 6, save the project in LiveCode's file format, and continue in a recent version of LiveCode.
HyperTalk and LiveCode aren't 100% compatible (probably around 80%, less if you used a lot of XCMDs since they aren't supported), but if you have an old stack you want to modernise, LiveCode is a great and affordable (it's GPLv3, with a commercial offering if you need to publish closed source projects) way to do it.
The best resource[1] on converting a HyperCard stack to LiveCode is by Jacqueline Landman Gay of HyperActive Software[2]. I believe HyperActive can also do consulting and conversion work for HyperCard stacks to LiveCode.