Worth noting there was a HN discussion on it from 5 months ago. [0]
I got the impression that ludde (the author of TunSafe) seems to think that people should trust him because he wrote uTorrent and he is, for reasons not specified, opposed to releasing it open source and suggests that the author of wireguard has a "general dislike against non open-source applications."
For what it's worth I really cannot understand the mentality that would lead to you creating a high-quality, benign VPN client that you have no intention to charge for or sell and not wanting eyes (which have certainly been offered) to look over it before users rely on it.