If you watch their videos, they explain it. They don't want to call it a free product because they're working hard on it and should be paid for it. But it is a perpetual trial license for those that don't have the means or ability to pay.
How is it suspect? They call it source first or some bullshit but the point of the liscence is to stop people from putting fake futo apps with ads on the play store.
But the code is still completely open, you can look at it as much as you want