Hi,
We do not use transifex, this is paid comercial service, and we do not have resources to use it effectively. Frankly, for our needs any text editor and average target language knowledge is enough.
Anyway, FA is open project, so if you wish to contriubute you are welcome to send your translation. on contriutions@frontaccounting.com.
Keep in mind there are two separate *.po files to translate, main for the application and separate for installer.
J.
PS As far as I know there is no Vietnamese translation in official FA repos for now, so I'm not sure where you seen Google translation. Anyway you are welcome to provide one for FA vietnamese community:)