From version 1.0.5 the game supports 3rd party translations, this is how to do it:

a) Download the current english strings from here:
http://planetbase.madrugaworks.com/files/strings.zip

b) Rename the files replacing "en" by your language 2 letter ISO code, for example for russian this woulld be "ru_main.xml", "ru_tutorial.xml", "ru_help.xml"

c) Translate the files, note that the "language_name" string in "en_main.xml"
is what your laguage is going to be called in the settings screen

d) Make sure you save the xmls as UTF8

e) Put the files in My Documents/Planetbase/Strings

f) Now the new language should appear in the settings menu

We will probably add proper support for Steam Workshop to download new languages at some point, for now you can just reply to this thread and post your translations here.

Thank you!