I get the math reference, but I'm not sure about the language joke. ???
It's entirely dependent on how you read it "literally, apparently"--it is apparently a literal approach to the old forum, which is wrong because the new forum is actually different, or "literally apparently" in which case "literally" modifies "apparently" instead and the implication becomes that the approach is only apparent in a literal sense (ie- only in terms of appearances: the color scheme, etc.). It plays off the fact that the words literally and apparently both have softer less literal senses (literally, used incorrectly as an intensifier; apparently, used correctly to mean "so it seems" in an abstract way that might not have anything to do with literal appearances).
It is not a "good" joke per se as it functions only within the realm that one might misunderstand the intent, hence the lampshading. :P