FuseBuilder 4.1 Edition is not being released under the 'honor ware' scheme as FuseBuilder 1.3 was. If you wish to download it you must have a full Multi-User License for its use.
However, you can evaluate FuseBuilder 4.1 online, and even create your own project to test out the new features! Simply go to online.fusebuilder.net and use the same username and password you use in the main portion of the website. Your online project will not be deleted, and when you do decide to upgrade your License, it will be emailed to you along with the application file.
If you can't rememember your login information, you can click on the "Password Reminder" link on the main website's sidebar.