Open source would be rather pointless here. The hardware is expensive, probably undergoing constant modifications of one sort or another. Software changes come from actual field trials and not from the kind of testing that can be done by just any interested person. A solid core of a few full-time programmers is probably more usefully employed in actual programming, not in screening contributions of mixed value from outsiders of whom they know little.
Might be different once other people have their own qualified cars, but not before then.