Responsive version of Thematic?

You might want to ask on their forums —

https://thematictheme.com/forums/

There is a version based on HTML5 boilerplate that you could make responsive.

https://github.com/sams/Thematic-html5boilerplate#readme

yes, all thematic questions should be on the thematic forums. you are free to make your child theme responsive.

i made some stylesheets that will make things somewhat responsive, but they are a bit out of date and should be made to be mobile first:
https://github.com/helgatheviking/Thematic-Adaptive

a couple other thematic forum folks have released responsive child themes that you can find in the forums.