...I thought I'd give Quicklisp a spin. After all, parsing some XML and sending HTTP requests are no big deal in Common Lisp either, and an OAuth library is available, too. With Quicklisp, all it should take was write some glue code to connect DRAKMA, CXML, cl-ppcre and cl-oauth. Installing the bunch should be a matter of loading quicklisp.lisp, then typing (ql:quickload `("drakma" "cxml" "cl-ppcre" "cl-oauth")) and watching the show scroll by.
And hey, it worked right away. I even embedded a web server in the gateway application so that it can be monitored by the system status monitors provided by my hosting provider. All in all, rewriting the thing in Common Lisp and deploying it took no longer than two hours, and the source is not significantly longer than the Clojure version either. Furthermore, the new gateway properly deals with non-ASCII characters. Embarrassingly, the Clojure gateway was buggy in that respect and never properly twittered the titles of my own blog posts. Thanks, Zach!
I hope other people find it just as easy.