I just got it to work. I needed to rename items similar to @gregfielding.
1. edit the file bbpress.pot file in poedit.
2. create the folder “bbpress” in the wordpress content languages folder. Make the languages folder if you need to so your path looks like this: wp-content/languages/bbpress
3. save the edited bbpress.pot file as bbpress-en_US.po
4. upload the created po and mo files to the bbpress folder in lanugaes. reset your cashe to see it working
Greg it looks like you were close but you have a dash instead of an underscore in the filename. I’m assuming the filename is also case sensitive.