As our ongoing effort to help internationalize SMF, we have added multi-language support to the customize site. This means, that soon (it could be now!) you will find the customize site translated into your language.
Our language translators have already started translating and the first pieces of translations where just added today. If you want to help out with translating, please see our announcement topic
in regards to details of how to join.
So what do you have to do? Well nothing (Say isn't that easy). The customize site uses your selected language from your profile. This also includes our language drop down located on the community forums.
While we have translated the customize site into other languages, we still will expect mod and theme authors to be able to speak enough English with our Customize team. This doesn't affect those using customizations although.
Please do not give me to much credit for this, all I did was add a couple lines of code into the customize site in order to give it multi-language. It is our translators who are working to help translate the customize site. So please give them the thanks and kudos for their work.
As a final note. We are working on adding language support for our main site. But this is a work in progress currently.