While it will render fine it's technically invalid if you serve a xhtml1.1 page as text/html. Most (all?) browsers won't have a problem with rendering xhtml1.1 when served text/html. Just means it will be rendered tag by tag instead of as a structured document and you lose the main benefits of xhtml over html: the browser checking for errors in the page and mixed namespaces.
Even though IE7 still wont support application/xhtml+xml I try to keep up with web standards. Who knows, if enough websites begin to use it they might update it. Probably just wishful thinking though.
Anyway, according to w3c you
"Should Not" serve XHTML1.1 as text/html.
To be honest though it's just nitpicking. But so is validation really
It doesn't really matter how you serve xhtml since (if it's valid) it should render almost identically.(
this article lists any potential problems with serving as application/xhtml+xml.)
But if you've gone to the trouble of making your page validate you may as well go all the way and compltley follow standards.
As for the calendar templates I'd just leave them. You mentioned it was xhtml1.1 on the page. People can always change the doctype and <html> tag to conform with XHTML1.0 if they wish. Although you might want to put a note in the readme about that.
Wow, I diddn't intend to write anything near that much.
