I have no java (programming) experience, and it took me ~45 s:

#apt-get install closure

#closure

user=> (+ 2 2)

4

Most of that 45 s was waiting for apt-get.

Now it's not going to be this easy on platforms that don't have such nice package management (e.g. Windows). Furthermore, Raphael_Amiard makes a good point that there's a lot more infrastructure that has to go into web application development (or any other kind of application development, for that matter) than computing the sum of 2 and 2.

Nonetheless, it just doesn't seem that hard. At worst, put a "clojure /path/to/project.lisp" in rc.local or equivalent.

(Caveat: my web development experience consists entirely of a couple of toy projects I ran on my laptop for my own amusement. Take all this with a grain of salt.)

EDITed for formatting.