Re: Add Register link
Looks like the text is actually provided by bb-includes/functions.bb-template.php, and the text depends on if you’re logged in or not.
Not logged in shows this:
('You must <a href="%s">log in</a> to post.')
I’m not sure how you would modify that to display what you want, without modifying this core file. Modifying core files makes it troublesome to upgrade to new bbPress versions.
What version bbPress are you using?