Seems to me that most people who do homebrews import/appropriate stuff from published source material all the time. And a lot of games I play that are in homebrew settings adapt published material and modules with great frequency.
Granted, this is one individual's experience, and not necessarily reflective of the greater gaming community...but given how much work developing a setting is, and running a game is, I suspect it's fairly common practice to find ways to use quality published material and tweak/adapt it rather than start from scratch every single time.
Can't decide if troll thread or not.