[yucca]

You can export OF data as a CSV, and import the CSV into OP (I suggest doing this with an empy OP file). To reverse the process, you should export from OP to OO; and, according to the OF docs, reformat in OO to kGTD format, and then import into OF. Never tried the full round trip myself.

I tend to do initial group (as opposed to individual) project planning in OO anyway; but, other than for initial planning, once you move the data to OP you are committed to keeping it there. IOW, OP does not appear to support ping-ponging the task list back and forth between OO and OP.