Yes, you can connect without a password as long as there's another user physically using the computer and they authorized the screen sharing request (see below).
Jump Desktop however does not allow unattended access to a computer without a password set. For unattended access you must log into the computer using a user account that has a password set. This is a security measure to protect your computer from unauthorized access.
Tip for Windows users: If you don't want Windows to prompt you for a password after every reboot, you can set it to automatically log you in on startup. Learn how to do this here: Turn on automatic logons in Windows 10 (Windows 7 here).
Password-less Screen Sharing
If you want to connect to someone else's computer without a password, please ask them to install Jump Desktop Connect on their computer and send you the Screen Sharing link. You'll be able to connect to their computer one they authorized the screen sharing request.
Alternatively if you're already an authorized remote access user on their computer, you can use the Ask to share screen button when you try to connect to the computer.