Yeah, you need a machine running the relevant game to export its data files. But, it's possible to take the data files from one machine and drop them into the same game on a different machine and get everything working. There are basically five files you need, but I don't know exactly where they're stored on a Mac: data.dat, hold.dat, player.dat, save.dat, text.dat. One or two of those may be missing if you don't have e.g. any self made holds, but I'm not sure.
So you have a couple of options I can think of:
1) Grab the OSX Intel binaries from
http://forum.caravelgames.com/downloads.php for KDD/JtRH/TCB and install those on your new machine -- they should still work. Then drop in the dat files from your old games and see if they still work. This will depend entirely on how DROD treats the .dat files; I don't know if they're compatible across platforms. But if this works, you still have everything on the same machine and you can do the export if you want.
2) If that doesn't work, try to get your hands on a machine which can run the older PowerPC binaries. That might be a friend with an older Mac, or get a trial of once of the virtualisation products and install OSX 10.6 if you still have a disc (10.4 to 10.6 included Rosetta, which allows running the old binaries on new hardware). Copy the dat files in and do your export.