“May” is indeed the operative word - their liability could be all over the place.
If they’d hired him as a test pilot for their in-house rocket program, then their liability should run deep. If they covered it in a such a fashion that they had no influence on the project, then their liability should be zero.
[BTW, I’m looking at ‘liability’ in an ethical, not necessarily legal, sense.]
But suppose they offer to sponsor an existing rocketry program? This was his second proven flight, and his claim of an earlier one sounds credible. He was already committed to continuing his efforts. Sponsoring him wouldn’t cause the crash, it would only speed up his timetable. If anything, extra funds should ease the need to cut corners, increasing his safety. In my book, they’s still be morally off the hook
But they walk a fine line!