The usage of yEd is free of charge and one can even make use of yEd in a commercial environment for free.
yWorks grants you the right to use yEd as an application to create diagrams. This right comes for free for anyone that adheres to the yEd Software License Agreement
. E.g. you are not allowed to distribute yEd on your own or use it in an automated process.
The diagrams that you create belong to you. You can use your diagrams in any way you like. For example, you can use yEd to create a diagram that is then used by your company or institution to enhance product documentation, or to better understand internal processes.
This answer applies to the desktop version of yEd
only, the usage of the web-based version of yEd
(called yEd Live) is governed by separate license terms!