From Swahili wikipedia's page on Maharagwe:
Maharagwe (pia: maharage) ni mbegu za mimea mbalimbali (miharagwe) kutoka familia ya Fabaceae lakini mara nyingi sana Phaseolus vulgaris.
From what I gather maharage is the Tanzanian spelling, and this is (mostly) a Tanzanian Swahili course.
From my time in Tanzania I only saw it written as maharage, so I'd agree with juryrigging!
It should accept both whenever we have to type it, but maharage is perfectly fine.