How can users communicate with a Bot Engine bot? Since wit.ai is part of Facebook, I naturally wonder if these bots will be locked into the Facebook platform.
Bot Engine is not tied to the Facebook platform.
It exposes an HTTPS API that you can use from anywhere. Slack, the command-line, Messenger, a VR app, etc.
We don't make assumptions on your platform.
https://wit.ai/docs/http/20160330#converse-link