▁of ▁the ▁K ▁Des ktop ▁Environment ▁ 2 ▁series . ▁All ▁releases ▁of ▁K ▁Des ktop ▁Environment   3 ▁were ▁built ▁upon ▁Qt   3 , ▁which ▁was ▁only ▁released ▁under ▁the ▁G PL ▁for ▁Linux ▁and ▁Unix - like ▁operating ▁systems , ▁including ▁Mac ▁OS ▁X . ▁It ▁is ▁marked ▁stable ▁running ▁on ▁Mac ▁OS ▁X ▁ ▁since ▁ 2 0 0 8 . ▁Un like ▁K DE ▁SC ▁ 4 , ▁however , ▁it ▁requires ▁an ▁X 1 1 ▁server ▁to ▁operate . ▁ ▁In ▁ 2 0 0 2 , ▁members ▁of ▁the ▁K DE ▁on ▁C yg win ▁project ▁began ▁port ing ▁the ▁G PL ▁lic ensed ▁Qt / X 1 1 ▁code ▁base ▁to ▁Windows . ▁ ▁Four th ▁series ▁ ▁K DE ▁Software ▁Comp ilation ▁ 4 , ▁first ▁released ▁on ▁ 1 1 ▁January ▁ 2 0 0 8 , ▁is ▁based ▁on ▁Qt ▁ 4 , ▁which ▁is ▁also ▁released ▁under ▁the ▁G PL ▁for ▁Windows ▁and ▁Mac ▁OS ▁X . ▁Therefore , ▁K DE ▁SC ▁ 4 ▁applications ▁can ▁be ▁compiled ▁and ▁run ▁n atively ▁on ▁these ▁operating ▁systems ▁as ▁well . ▁K DE ▁Software ▁Comp ilation ▁ 4 ▁on ▁Mac ▁OS ▁X ▁is ▁currently ▁considered ▁beta , ▁while ▁on ▁Windows ▁it ▁is ▁not ▁in ▁the ▁final ▁state , ▁so ▁applications ▁can ▁be ▁un su itable ▁for ▁day ▁to ▁day ▁use . ▁ ▁K DE ▁SC ▁ 4 ▁includes ▁many ▁new ▁techn ologies ▁and ▁technical ▁changes . ▁The ▁center pie ce ▁is ▁a ▁red