Earlier quoted context omitted.
It's been in Debian for more than 20 years (see changelog here: https://tracker.debian.org/media/packages/s/stardict/changel... ). It's not clear to me if said "autosend off clipboard contents" has been in there the whole time though.
Data leaking bug reported as early as 2009: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=534731 , so it's not looking rosy.
Personally, if I was using (or a maintainer of) a dictionary tool which autoreads the clipboard (or any dictionary tool), I'd be checking what it is doing and considering whether it is what I would want to use.