That would depend on how much of the web environment you want to reproduce and what language we're talking about. The original Oberon fit into some 5500 lines of code, if I'm not mistaken. That's sort of smaller than Apache httpd. It's even smaller than nginx and lighttpd. And we're still talking about pretty weak languages, have you seen some of the self-hosting metacompiler stuff? (META-II, TREE-META, OMeta etc.) Don't forget that the design of the reference Go implementation is actually pretty close to the Oberon tradition of making things simple.