The login page asks for the "username". I would like it to say "username or password" as shown in the image of the attached file. Is there a simple way to do this without from within wpForo without installing a plugin?
Only changing the word won't make changes in the system, if you want to make some customizations on the Login/Register pages, I recommend you to disable wpForo Login/Register option and use WP Login/Register plugins.
To Disable wpForo Login/ Register, go to Dashboard > Forums > Settings > Features Tab and disable these options
Replace Registration Page URL to Forum Registration Page URL
Replace Login Page URL to Forum Login Page URL
Replace Reset Password Page URL to Forum Reset Password Page URL