The software is licensed under GPL 2.0 which shouldn’t preclude any specific type of use.
Now, there are the “Terms of Service” which are supposed to be user-editable in any Discourse installation, but due a bug currently aren’t (as far as I know this is still broken). I’m not too familiar with their contents.
Otherwise, generally, developers of software with Free or Open Source licenses, don’t have any way to specify what people do with that software.