I have totally hypothetical (but related) question, though: to what extent does a site's CSS need to be changed, for that CSS to be one's own? I'm just not sure to what legal limits people can use your site to save CSS code from other websites that aren't their own? Again, I have no expertise in this particular question, but maybe you want to include a small disclaimer...?
Good idea on the _appends_ - who wants to save the entire code for each iteration, rather than just the changes? (hitting myself over head) haha About Wordpress: their explanation seems more marketing-related rather than practical: http://codex.wordpress.org/License Maybe going GPL reflects a core change in their business model, now that they're hitched with all the Windows Live blogs?