Sorry for the late reply.
The translation is fairly simple, take a look at some of the existing langauge files in the lang folder.
For example take en_us.inc and en_gb.inc (English US and English UK)
Use these as your starting template for the new language translation.
Save a copy as say pt_br.inc (or use the existing file, but this may be incomplete, see below) then translate all of the lines as per this example..
$GLOBALS["lang"]["Home"]="Inicio";
(OK Bad example, that's Spannish, but $GLOBALS["lang"]["Home"]="Home"; doesn't work so well
)
Furthermore if you set $language_learning_mode==1 in include_lang.php and then run through all of the program options first, this should so far as I recall add all of the text for the options to the current language file, in English. Once you have done this, then modify the language file translating all of the text as per the above example.
Once translated, post the translation here, and we will add it to the SVN.
Let me know if you run in to trouble or need any further assistance.
Thanks
Andrew.