▁impossible ▁to ▁port ▁Build ▁to ▁a ▁mult it ask ing ▁OS , ▁as ▁it ▁needed ▁a ▁large ▁cont igu ous ▁block ▁of ▁memory ▁that ▁wouldn ' t ▁be ▁available ▁in ▁a ▁mult it ask ing ▁environment . ▁This ▁statement ▁did ▁not ▁hold ▁up ▁to ▁scr ut iny , ▁as ▁all ▁modern ▁operating ▁systems ▁use ▁virtual ▁memory ▁which ▁allows ▁apps ▁to ▁get ▁cont igu ous ▁logical ▁memory ▁without ▁using ▁cont igu ous ▁physical ▁memory , ▁but ▁conventional ▁wisdom ▁of ▁the ▁time ▁was ▁that ▁port ing ▁Build ▁to ▁such ▁an ▁OS ▁was ▁un fe as ible . ▁▁ ▁Duke ▁N uk em ▁ 3 D ▁source ▁release ▁ ▁On ▁April ▁ 1 , ▁ 2 0 0 3 , ▁after ▁several ▁years ▁of ▁claims ▁to ▁the ▁contrary , ▁ 3 D ▁Real ms ▁released ▁the ▁source ▁code ▁to ▁Duke ▁N uk em ▁ 3 D . ▁Not ▁long ▁afterwards , ▁both ▁Ryan ▁C . ▁Gordon ▁and ▁Jon athon ▁F ow ler ▁created ▁and ▁released ▁source ▁ports ▁of ▁the ▁game , ▁including ▁the ▁Build ▁engine . ▁It ▁was ▁possible ▁to ▁play ▁Duke ▁N uk em ▁ 3 D ▁well ▁on ▁the ▁N T ▁line ▁of ▁Windows ▁( including ▁Windows ▁ 2 0 0 0 / X P ) ▁and ▁on ▁Linux ▁and ▁other ▁Unix ▁operating ▁systems , ▁and ▁interest ▁in ▁the ▁source ▁ports ▁so ared . ▁▁ ▁ic cul us . org ▁port ▁ ▁Ryan ▁C . ▁Gordon ▁( ic cul us ), ▁with ▁the ▁help ▁of ▁others , ▁made ▁the ▁first ▁port ▁of ▁the ▁engine