>I'd like to help with translating Trinity into Polish language.
>Just plain text files or some really simple dev tools.
Hi Janek,
as a start, you can checkout the tde-i18n folder for the polish translation or download specific files from the GIT repo web interface (http://git.trinitydesktop.org/cgit/tde-i18n/tree/tde-i18n-pl) and update them.
.po files (in the "messages" folder) are plain text files. You can use Kate to edit them.
.docbook files (in the "docs" folder) are used to create the handbooks and they are also plain text files, even though in docbook format.

.po files and .docbook in general need to be updated (even the english source version), but at least you can start to review them. If you have updates, please open a bug report (something like "updated polish translation files" and attached translated files when they becomes available).

Cheers
  Michele