The main site is located here: molly.im
The first paragraphs on the donation page:
The goal is to build a secure messaging app with integrated support for Monero payments and a decentralized backend.
The application will be based on the Signal fork Molly.im (henceforth ‘Molly’) but with a privacy-focused backend that allows the user to sign up anonymously (without phone number), encrypt their local database with passphrase encryption, RAM shredding, and more.
Monero features will include the ability to set up a XMR wallet, send and receive funds, keep track of the balance, and review the history.
That comment does not make me confident in the developer.
No, the developer is assuming there isn’t such a vulnerability. No one can know if there is or not. Applications are complex, there’s a lot of code, a lot of room for a vulnerability to go unnoticed by even a skilled programmer. OpenSSL was a thoroughly reviewed open-source library that had been widely used for a long time and heartbleed still happened.