That's about the long and the short of it, although some the info differs from what I have - but then the info I have was written by a journalist so it's bound to be wrong..
My info says that its name (MAX) stands for Mother's Automotive EXperiment, and it's a high-mileage (per gallon I assume they mean) lightweight car that has been hand-built by Kinetic Ltd (hence my reply to woodinsight) for whom Jack McCornack works (or even owns maybe?).
As you say it has a 32 bhp Kubota industrial diesel engine and will do 90 mph. The journo said it was "modelled after Le Mans racers from France", showing perhaps that she knew where Le Mans is situated but little else...
McCornack says this model is a research and development car but interested persons can purchase kits to build vehicles from Mother Earth News Magazine.
So there you are, tree-huggers, if you want a car that looks like it goes but doesn't but at least won't hurt you too much in the wallet, put on that old raincoat, turn up the collar and nip out to buy a copy of Mother Earth News then send off for a kit, although where you're going to get a clapped-out Lola body from I'm not entirely sure...!