MyForum Plugin (on Liferay's MarketPlace)
This Plugin developed by Liferay 6.1+ allows you to create different forums with different categories of arguments. In most every forum can be associated with a community of users. All easily manageable from the control panel of Liferay.
Users can post text only (no images or files) and can only post in forums associated with them.
MyForum - control panel
MyForum - community settings
My Forum - user portal
MyForum - posting