Nope, you need to have contents in Catalan in your .cat site, not for six months but forever. I couldn't find this 6-months clause anywhere, and the terms don't mention it at all: http://fundacio.cat/ca/domini/sobre-el-cat/normativa

Furthermore, they clearly say that violation of the only usage restriction (contents in Catalan) can result in your domain being suspended.

edit: Just a little correction to your text in Catalan: L'idioma català és una llengua bonica. ;)