the "sdk" is open source, but flex builder isn't (and they managed to break stuff that worked fine in eclipse). and have fun trying to get the flex builder plugin to work on linux, or even get the sdk working completely on linux.
I mean, come ON! A plugin for freakin' word-wrap?!
You need to install a plugin to enable this. Granted, this is a limitation of the underlying Eclipse on which it is built, but I was using Flex Builder, not Eclipse, so my beef stands.
Citations: http://forums.adobe.com/thread/451245, http://www.communitymx.com/abstract.cfm?cid=E0D9F