The related videos added by YouTube to a clip can be cut off in a browser by adding "?rel=0" to the video link. This step, however, currently can't be used in eMagStudio.
When a YouTube video is embedded in eMagStudio, the 11-digit YouTube ID is used which even doesn't allow adding this piece of code. We have fixed this issue, and it is included in eMagStudio 4 and newer.
To fix the older eMagStudio installation, do the following:
Download the attached file
On Windows, go to "C:\Program files (x86)\eMagStudio\reader\pubData\plugins\" folder
On Mac: "/Applications/eMagStudio.app/Contents/Resources/reader/pubData/plugins"
Copy existing "VideoPlayerDeclaration.swf" to a safe location
Replace it in the "plugins" folder with the file you downloaded
The related videos should be disabled now in all YouTube videos you will be embedding.