The Desktop license is that you can download and install Turbo Tax on 5 computers that you own. You are not suppose to share it. They are enforcing it more now. See the End User License Agreement, scroll down to Section B Software and Services Terms
#1 Supplemental License Grant and Restrictions
https://turbotax.intuit.com/corp/license/desktop.jsp
No, they will not be able to see your info and returns from another computer. The returns are only kept on the computer they were done on. They are not stored or saved on Turbo Tax online. They can still use their account to efile their own returns.
