[@_ck_ Participant 16 years, 1 month ago]

Poedit will automatically re-save the .mo file when you edit and save the .po file by default unless you’ve changed the default settings.

the mo file is in here, it’s all you need

http://ayudawordpress.com/?dl_id=96

in bbPress 0.9 put it into bb-includes/languages/

in bbPress 1.0 put it into my-languages/

and change in your bb-config.php

define('BB_LANG','es_ES');