Nice idea but Facebook is not a save site, the password can easily be hacked, that is my main concern because it is possible for someone to intercept ones transaction. I like to also know if this project is an open source project so that people can look into tthe whole code and see if their is no bug inside and even a virus fro your own part
Finally, a real good question.
When entering the chatbot, you are asked to enter your personal PIN code. This PIN code is separate from your Facebook password (of course) and is used to encrypt your Bitcoin wallet. The PIN is entered in a "web view" (a browser window) and all encryption/decryption stuff is done on the client side, as with other online Bitcoin wallets. It can be hacked for sure by Keyloggers, but that's the same with other Wallets.
The code can be inspected in the browser, there is no code scrambling used, so yes, it is "open source". It is currently not public in Github, but this wouldn't help anyway because you could not tell if the code from Github is actually the same as served within the application itself.
I posted a short Screen video on the Facebook page so you can see how it works. For those without Facebook account, it's on Youtube now as well:
https://www.youtube.com/watch?v=4lDILIkOtjw