Quote Originally Posted by Jarkko View Post
for example the flashcanvas doesn't work in quirks mode, resulting that you can't develop anything with canvas-elements which would support any IE-browsers.
Yes, that would be a problem.

You can change it. But you'll have to touch a lot of files to make it happen, depending on which pages you intend to add canvas elements for. And test that you've not broken anything else that might have been depending on the original doctype.

As I said before, v1.6.0 is being updated to use HTML5 ... and unfortunately it's not a simple matter of touching just a couple files.
In the meantime, make whatever changes you need for yourself, and be sure to test that you've not broken anything else in the process.