Yes! Copy the code for bbPress login (html) and paste it into a widget, it should work.
You should consider integrating both WordPress and bbPress to have login synchronization (loggin into one will make you login for the other too and the same goes with logout)
my bbpress and wordpress ara just integrating, if i’m login with wp i’m login also with bbpress, but while the registration with bbpress the user must insert name, email, site with wordpress the user must insert only a nickname and email…I want to menage the registration only with bbpress….I try to put the html code for login but there is a little problem, until the user isn’t logged in the sidebar there is the login form, but when the user login in the sidebar remains the login form instead “Welcome, user, ecc…..”
There is another way for put login form in the sidebar?
thank you
but while the registration with bbpress the user must insert name, email, site
Only username and email are required.
ok but I want that the user put also other information…
I don’t like the wordpress profile manager, i prefer the profile manger of bbpress than i want that all user access only to bbpress profile manager.
U found this topic https://bbpress.org/forums/topic/load-bbpress-into-wordpress it can be a solution but when I put require_once(‘/bbpress/bb-config.php’ ); i recive a blank page… 
any solution?
kikko088
