It's from Castaway Stories! There's a ton of Castaway crap on MATY, but the ruins are from this post specifically-- scroll down a bit, they're in there. (However, the first post? Has some coconut trees for you. Somewhere on InSim there's a mod to make the harvestable trees harvestable for edible fruit instead of just cash or food points, but I haven't tested it enough to recommend it.) I kind of completely love Castaway crap.