This is what I did, on a Mac, in the Terminal
(where there is a file or folder in the command, you type it, or you can drag it in from the Finder into the Terminal window, and it will expand to the Unix path for it.)
cd /path/to/xfdf-file/
grep "\[" movie-clipnotes.xfdf | sed s/">"// | sed s/"<.*"// | sed s/"
"/" "/ > movie-clipnotes.txt