Messages are not end-to-end encrypted, and this is not an anonymous system. See below for more details. We use the term 'secure' here to mean that we do not use plaintext transports.
Although to my admittedly meagre security knowledge, I would've assumed that "no plaintext transports" would mean it was encrypted end-to-end.
I really really really don't recommend outsourcing your security architecture to interested passers-by if that's going to be a core feature of your project.