Yes, it is the MAG-Fokker Triplane
they built at least tree of them (90.01, 90.02 and 90.03) between July and December 1917.
MAG Fokker 90.01 was a triplane with inline engine, no photos are known
MAG Fokker 90.02 was actually a Fokker V.4 without the external wing struts,
MAG Fokker 90.03 had a 150 HP La Rhone and it was a triplane with the fuselage lengthened by 55 cm: the long fuselage is visible in the photos.
For further documentation you can refer to the "bible", i.e. Grotz, Haddow, Schiemer "Austro Hungarian Aircraft of World War One", page 340-342
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