Oh not at all, you can use it for other applications but the script would need to be altered to suit your needs.

Emma explains the format of the data being submitted to the php script here:

https://gitlab.com/edgyemma/Postmill/blob/master/docs/webhooks.md

In this case, the script only handles new submissions and formats the data into a $text variable, then sends a POST request to the bot with some other bot data.

You can format the data any way you want and post it to any server you want, it would work the same.