Wanted to share that the 3.x version of twine-utils is now able to parse Twine 1 TWS files. I think, but I could be wrong, that this is the first utility to be able to work with them. (It can also now work with Twine 1 published HTML, but I believe tweego has been able to do this for a while as well.)
I don’t expect that there are many people looking to make the leap from Twine 1 to 2 today, but it might be useful for preservation purposes.
I also put together a simple web frontend for the library here that in addition to exporting to current Twine or Twee, can also give you a straight JSON export.