Is it possible to create Ubuntu Shirts ( Merchandise )
Solution 1:
Yes it is possible, so long as you follow the Trademark policy, the trademark page lists the policies (community advocacy probably applies to your activity).
http://www.ubuntu.com/aboutus/trademarkpolicy
Additional information is provided on the following links
http://design.ubuntu.com/assets/ubuntu-logo
Downloads - http://design.ubuntu.com/downloads?metadata=element-logo+brand-ubuntu
If you have questions, Contact Canonical Legal.