by default, post author's name is linked to profile page. and by default, b2evolution shows user login on profile page. this raises some security concerns - you don't want the public to know what is your login and you don't want to make it easier for hackers to hack into your system.

there is no setting in the backoffice to control this. it's all done in the skin.

the file to edit is _user.disp.php. if  this file doesn't come with the skin you're using, copy this file from the skin root directory to the skin directory. just search for the word 'Login' and delete the code, and delete anything you don't want to be shown.

if you want to link author's name directly to a website instead of user page, read this.