Would love to see ride hailing apps in open source, since most of them are losing lots of money and may shut down.
This is a good wish. It's going to be challenging without a central authority to be fair to both riders and drivers.
They lied on the app about how long the cars would arrive, so people opted for Grab when booking on both platforms. They'd offer bonuses to drivers that were impossible to obtain (e.g. drive to a location without road access). They'd offer X in bonuses then pay out 0.7X, taking a cut from the promised bonuses and from tips. Uber would loan money to drivers and then let the drivers they banned keep the loan. Grab would withhold payment to drivers, ban drivers who got less than say, 4.5 rating, then not pay out the drivers they banned.
All fair game, all legal. The rough play helped them win, or so they think.
I've had requests from 3 people who wanted to build a ride hailing app. It's not worth the time and I'd discourage anyone who thinks they could stand up to Grab with just implementation ability. But if there was a code base, I'm sure some would be happy to take the mantle.