The NGS (New Generation Server) code is using gettext to provide with automatic internationalisation of messages and texts used in the perl code and templates.
a .pot file is provided with all the strings used in the server. They are in english.
If you want to translate them, go to the transifex page here https://www.transifex.net/projects/p/musicbrainz/ and create an account. Then ask to be a member of the team of the language you speak or ask for the creation of a new team if it doesn't exist yet.
This wiki is the perfect place to discuss specific languages translations issues such as glossary, or right-to-left required patches etc.