Hi Matt,
I am a programmer with experience of 10 years. I provide support the Russian-speaking users of bbPress since 2006. I think, I could help in the further development of bbPress.
See https://bbpress.org/forums/topic/php_e-issue#post-16264
But there instead of wp-blog-header.php and wp-wp-blog-header-bb.php must be used wp-load.php and wp-load-bb.php files.
I have the same problem even after installation on localhost (WP 2.7 + bbP 1.0a3)
Use PoEdit:
msgmerge --no-fuzzy-matching -o ru_RU.po wp_ru_RU.po bb_ru_RU.po
All calls of functions “__()” and “_e()” should be with textdomains.
For example
_e('Hello!', 'onlinelist');
Just add new page with slug, as in the folder your bbPress installation.
For example, “forums”.
2ganges
It is translation is a .po file. See in archive (latest.zip).
But there are some modifications.
Excuse 
The plugin is available for download here.
Плагин можно загрузить здесь.
This hacked version not works for cyrillic.
I’ve make a plugin for automatic transliteration of tags.
The plugin is available for view here and for download here
Этот плагин действительно не работает для кириллицы. Вместо него я сделал плагин для автоматической транслитерации тэгов.
Плагин можно посмотреть здесь и загрузить здесь
There is an error in /bb-includes/template-functions.php file .
In that file find
($smallest + ($count/$fontstep)."$unit;'>$tag n";
and replace it with:
($smallest + (($count-min($counts))/$fontstep))."$unit;'>$tag n";
