You can export your projects by going to the menu "File > Export" and select just the projects you wish to export.
Alternatively, you may wish to make a copy of all your data, TidyCards stores it's database in ~/Library/Containers/TidyCards. You can control-click on this folder and choose "Compress TidyCards" to make an archive.
YES! I'm working on it right now, it's taking a while as I get to grip with making sync work.