from the WP org codex:
Using Localizations
In order to localize your installation of wordpress, create a directory named languages inside of wp-includes, if it does not already exist. Then grab the appropriate localization files from the Subversion Repository as described above. The main .mo file for the language should go inside the languages directory. Set WPLANG inside of wp-config.php to your chosen language. For example, if you wanted to use french, you would have:
define (‘WPLANG’, ‘fr_FR’);
i’ve this configuration on my MU+BP and all works fine.
The WordPress MU language file should be in /wp-includes/languages/ and you can change the language in your admin section of your wpmu install.
The BuddyPress language file (buddypress-xx_XX.mo) should be in /wp-content/plugins/buddypress/bb-languages/ the xx_XX should be the same as on the file in /wp-includes/languages/ since BP gets the language setting from WPMU…
You don\’t have to edit anything in your wp-config.php file!
All of this is for WordPress MU 2.7.1 and BuddyPress 1.0. I don’t know how it is with older versions…
HTH
Regards,
RuneG
Kogigr now you have buddypress-el_GR.po and buddypress-el_GR.mo in /wp-content/plugins/buddypress/bp-languages/ right?
in wp-config.php insert on line #77
define (\’WPLANG\’, \’el_GR\’);
and save…
I think this should resolve (BP side), however, looks for the translation of MU in greek.
I followed the link you provided and they share an “el.mo” file. I guess I shouldn’t have spent 7 hours last night translating mu..
Anyway, my problem wasn’t the file, I already had mine. The directory I’ve put it in is “/wp-content/plugins/buddypress/bp-languages/” and it’s named buddypress-el_GR.mo. I saw in another thread that the directory should be “/wp-content/mu-plugins/buddypress/bp-languages/”, is that my fault?
I also changed the language in the wp-config.php file to “define (‘WPLANG’, ‘el’);” and it didn’t work, so I created a folder named “languages” in “/wp-content/”. It still didn’t work.
@Kogigr;
AFAIK, you have to use the same language in WPMU as in BuddyPress. BuddyPress gets the language setting from WPMU. There is some info about the greek WPMU translation here, but I don’t read greek, so it’s not necessarily the info you need 
But you’ve named the file(s) right, you only need the .mo file in your bp-languages folder.
So basically you need to use the same language in WPMU that you want to use in BP. So get the greek WPMU translation, upload it to you WPMU install, and change the language in you admin section…
HTH
Regards,
RuneG
Ahhh, I found the error…
Some of the things I\’ve done on my installation was done before I translated and uploaded the .mo file.
When you do an activity, let\’s say you write on a group wire. The whole thing including the text wrote on the wire of the group is stored in the DB (in the table wp_bp_activity_sitewide), and thus if you change the language that will not change…
But when you do something new, then the correct language is shown (and stored in the DB).
So changing the language after you\’ve done something in your BuddyPress install is not a good idea 
Regards,
RuneG
Yea, I know. It _should_ work. But noooo 
It’s probably an easy answer to it. I just don’t see it…
Hope someone can give me some hints on what’s causing this. Thanks for your suggestions DJPaul and Arturo!
Regards,
RuneG
It looks like it *should* work. Guess we’ll have to wait to here from someone else who has done a translation if they get the problem.
@DJPaul
Yes, that’s the one, and 1019, 1043 in the same file and everywhere there is sprintf ( __(.......
And yes, it’s the .pot from the 1.0 zip.
Regards,
RuneG
No, wpmu is in english.. I renamed the files to buddypress-el_GR.po and buddypress-el_GR.mo but still no change. The country code and language code are correct, because I found them in wordpress documentation.
I still don’t know what’s wrong, though..
do you have wpmu in greek? save the lang file buddypress-xx_XX.po and the same .mo
xx_XX is language_COUNTRY for example it_IT (italian_ITALY).
bp-groups.php line 1005, right?
'content' => apply_filters( 'bp_groups_created_group_activity', sprintf( __('%s created the group %s', 'buddypress'), $user_link, '<a href="' . $group_link . '">' . $group->name . '</a>') . ' <span class="time-since">%s</span>', $user_link, $group_link, $group->name )
As Arturo’s suggested, check you are working from the .pot file that comes with 1.0. It’s possible it was changed since an older version thus your translation not being applied.
i’m a member of BP Italy and i’ve translated the 1.0 pot file and all is ok the string “… %s created the group %s..” is translated… do you have used the .pot file in the 1.0 zip file?
Hi all, and congrats on the 1.0 milestone!
I’ve translated the 1.0 into Norwegian, but I have a problem with translation of text that starts in the code with sprintf( __('%s created the group %s', 'buddypress'), $u.......
That text is not translated. The translation is there (in the .mo file) and everything else is translated just fine.
Does anyone have an idea on what’s going on?
Regards,
RuneG
Hi..
I translated the buddypress.pot file into greek, using PoEdit, and I saved it as buddypress-el.po . I then ran a command that converted the .po file into .mo . Now I had 2 files that needed to be uploaded to /wp-content/plugins/buddypress/bp-languages, so I did that.
Having uploaded the files, I edited wp-config.php so as to change the WPLANG value. The line looked like this \”define (\’WPLANG\’, \’el\’);\”.
Having done all this, the language is still english and I have absolutely no idea why that happens.
I\’d appreciate any help.
Liagk-
The primary resource for learning about translating WordPress files is here: https://codex.wordpress.org/Translating_WordPress
Also, some helpful forum threads:
https://buddypress.org/forums/topic.php?id=171
https://buddypress.org/forums/topic.php?id=1877
Finally, when you’ve completed your translation, it would nice if you would add and link in the codex: https://codex.buddypress.org/translations/
Something strange happening on my install.
I didn’t touch my computer for the day, and I only use my laptop to configure my buddypress install. But my buddypress is updated with the latest release, as of 29th. So my custom file and translation files are deleted by the buddypress update.
If my server is hacked, I’d know…but it’s only buddypress acting strange not wpmu or any other files on my host.
I totally forgot about the wp’s plugin up grade system that when you update plugins, old files are deleted once in order to install new ones.
What is written in the document is not exact, so make sure you backup bp-custom and your translations (po,mo) files local before upgrade via plugin’s system.
Since the language file you’ll be creating (and the bp-custom.php file that loads it) aren’t in the BuddyPress SVN repository or BuddyPress download packages they will not be overwritten when you upgrade to a new BuddyPress version.
2545516Inactive
I would also be interested in a language drop down in Spanish and Portuguese and probably could help with the translation if needed
About to start a danish translation of BuddyPress. Currently considering to use either LaunchPad or Pootle as our collaboration tool.
Anyone know if Dreamcolor expects to initiate the LaunchPad project:
https://translations.launchpad.net/buddypress or release the ownership, for others to use it?
Suggestion: why don’t we settle on the same tool to use, eg LaunchPad – would make it easier for other to take part of the work.
For all who are still having this issue. There was a bug fix 3 weeks ago that addressed this issue. See Changeset 1244. All widgets that come with BuddyPress were fixed with this revision.
If you are not running at least BuddyPress r1244, then you will still have issues.
Note: Custom widgets (3rd-party developed widgets), may or may not have implemented this bug fix. Therefore, if you are having translation issues with non-core BP widgets, you will need to contact the developer directly.
Some questions….
1) Remove all your bp widgets. (Done that)
2) Open translation.po
(Where is that file located?)
3) Find bp-core/bp-core-widgets.php (it is mentioned many times and write down the line numbers)
(Didn’t find it….) ??
4) Open mu-plugins/bp-core/bp-core-widgets.php
5) Translate manually the lines where the translation file was supposed to do it.
(Can anyone tell me the line numbers?)
6) re-upload mu-plugins/bp-core/bp-core-widgets.php
7) activate widgets that now will be named on your translation language e.g. “welcome” will be “Bienvenido”
send me a beer!
(Ill send you 20 beers if you help me) 
Thanks yall!!
thanks a lot! that page didn’t show up when I googled wordpress and pot …