Json jokes are not jokes only about json but it is list of jokes in json format. There is database of short jokes from several sources. If you will find some other good sources, please, send me a message or add comment to this post :).
You can use prepared python script get_joke.py for geting random joke. Other possible (easier) way is to visit the page http://zloutek-soft.cz/json-jokes/ (you will see new joke with every F5).
In my case I have calling python script in my .bashrc script (it runs always when the terminal starts in linux). So I can see short joke on the first line in my terminal. For better view and more fun you can use command like:
python /path/to/get_joke.py | cowsay curl -s http://zloutek-soft.cz/json-jokes | cowsay
Project is of course open source and you can visit it in gitlab https://gitlab.com/greg007/json-jokes