I guess I'm 1 of the few people who had no problems installing those modes!
In my personal configuration, my "Sketchbook location" is outside where Processing itself is installed.
And I've found out that those extra modes ended up installed inside a sub-folder called "/modes"
within my "/sketchbook" folder; rather than Processing's own subfolder "/modes", where the bundled ones
(java & experimental) are located!
Thus, I have sub-folders "/CoffeeScriptMode" & "/JavaScriptMode" in my "sketchbook/modes",
and "/java" & "/experimental" in "processing-2.0/modes/". They're not together!