>>105920641
Someone did write a *chan clone and you can fins it at khzae.net. his site is super slow but you can download the code. I don't know if it could handle a site as busy as the real 4chan but it works as a proof of concept.
Besides that I have found it enjoyable to shitpost on fidonet and the other BBS nets. It is almost like Usenet back in the day.