Well, this is strange. Today I posted a visual suggestion about the possibility to change your deviantART username after every six months and half a day later deviantART announced that you can now change your username after every six months.
Anyway, if you are interested in changing your username then you can now do it. Just go to your settings and you should find the right place from there. However as said before, you can only do it twice a year and you have to be a premium member for that.