Agreed. I would not consider running a closed source shell because it's not auditable.
Googling "security audit my code" finds several companies that offer such a service. My concern would be (aside from the admittedly non-trivial benefit of just having better code), would it make a difference to anybody that was on the fence about it? I suspect that the matrix of "potential customers" vs "what auditing service they'd trust" is large.
Thank you for the comment.