"NSIS 2.21" handles Breton!

NSIS: Nullsoft Scriptable Installation Software is used by AbiWord, eMule, FileZilla and other open source or free software to handle their installation.

You can have a look at the list of software whose installation is based on it, here.

It handles now Breton. This will hopefully allow very soon an installation of these software in this language.

Download the translation files here