Hello Alex about the confusing (at least for new beginners) parts of the language module creation, here are my notes:

....

3.  ... classprefix specified in point 1, to be point 2 .
4. 

• Edit modules/vendor/french/install/langs/en.xml file, by changing only the following:

  • change all language key prefixes to your own, for example from _bx_rsn_ to _vend_fr_
    (and we may  here add for the resources line make the changes like rs to fr Russian to French
    <resources name="ru" flag="ru" title="Russian">
    
  • change translations from Russian to 'French`

9. To package the module, run the following from your UNA root folder (it requires build.xml file which is in the UNA repository): /path/to/phing package_module -Dvendor=your_vendor_folder_name -Dmodule=your_module_folder_name
ZIP file for the module will appear in /packages/ folder in your UNA root directory.

* Here shall we copy the xml files that we translated from:
packages/en  to >>>>>      modules/vendor/french/data/lang/bx_albums
or the packing script does this?
* When we want to test installation of our pack, shall we first delete/rename the modules/vendor/ourlanguage directory to simulate someone who never ınstalled our language pack? If we dont delete / rename this directory can we install  the lang pack?
8. When new version of UNA is released you need to update module and add/remove/change some language keys. The list of changed language keys can be found in English module update files, also you can also use it as a template to create own language module update. For example the here is the list of changes from 9.0.0 to 9.0.1 for English language.
I found the update file and there are add and del commands in the xml file that shows me that the update script will work on this xml .  And there are same type of update files for the other modules.
I thing we need to create copies of these update files and translate them for instance
For English language:
/modules/boonex/english/updates/9.0.9_9.0.10/install/langs/en.xml    >> fr.xml
For albums module
una/modules/boonex/albums/updates/9.0.9_9.0.10/install/langs/en.xml    >> fr.xml
After that what to do? We will leave the new files there and when the users updates their modules will they automatically used?
We need detailed explanation about the update procedure here.