I want a to have a discussion forum, with forms based authentication mode and a registration module. (it will be done in a webPart) This forum includes topics, questions, answers...
I basically started with trying to configure FBA for sp2013, but doing this with activate the fba mode for the hole siteCollection, not for the specific discussion board that i want to use.
To be more clear, i want to have a discussion board that, if somone wants to add or answer a question, will need to autheticate using FORMS (FBA)
How can i achieve this please ? easiest way
So if I understand correctly, you want the discussion board available anonymously, but users would have to login/register to add or answer a question?
In that case you would turn on anonymous access for the site collection and give anonymous users read permissions to the forums. Then whenever a user accessed something that requires permissions (such as posting to the forums), they would be prompted to login if they hadn't already.
Now, i'm not completely sure that the SharePoint discussion boards support that level of permissions, as I have not done this myself, but that is how it would be done in general for SharePoint.
Also, if you are using SharePoint ONLY for the discussion forums, you would probably be better off with a discussion board only web app (http://en.wikipedia.org/wiki/Comparison_of_Internet_forum_software) - as they would be more fully featured and probably support what you want to do out of the box without much configuration.