Yes, guest attendees can share their screen without registering for an Amazon Chime account as long as the meeting host has Pro permissions.
There are several ways to share your screen.
You can also download one of the Amazon Chime desktop clients (Mac or Windows) from https://aws.amazon.com/chime/trial and install the application.
Choose Join a meeting without an account from the Welcome to Amazon Chime screen.
Enter the meeting ID and your name and then choose if you would like to use your audio or not.
From the Meeting window, choose Screen and choose to share your screen or window.
View the Amazon Chime User, Administration Guide and API Reference on the AWS Documentation site.
Find more information about the Amazon Chime solution, pricing, customer references, getting started, and other resources.