BuddyPress.org

So, I have wp+buddypress+my theme+plugins (=mo files) translated to 2 languages.

And I need to add new feature to my users… the choice to choose their language in registration page, and/or in buddypress profile settings (in frontend)

I do not need the WPML and similiar plugins, because I need only the switcher. And I am not going to translate posts or pages.
Somethink like this plugin, but better for buddypress usage:

fw-quick-langswitch

Thanks all for your help.