Thread:Skin talk:Foreground/Non-translated strings/reply

Hiya Micru, no it isn't. Foreground is the joint creation of Garrick van Buren and Jamie Thingelstad. I don't know if and to what extent support for Spanish is handled natively by the skin. Of course, MediaWiki comes with language settings of its own (you may also want take a look at the Universal Language Selector), but I guess you already knew that.

See also GitHub, where most of the discussion about the skin seems to take place. Hope that helps!