Ubuntu – Is it possible to create Ubuntu Shirts ( Merchandise )

You have the right to modify and redistribute Ubuntu under the GPL.

As long as you don't infringe any trademarks like 'ubuntu' or 'buntu' for example calling it 'Jorge ubuntu' without permission, or claim to be officially endorsed or assiosiated with Ubuntu / Canonical then you should be fine.

You should read this link for clarification and contact Canonical if you are unsure.
They were very helpful when we asked permission to use their trademarks.

Canonical have a couple of trademarks on the word "Ubuntu":

• http://www.ipo.gov.uk/tmcase/Results/4/EU004059119
• http://www.ipo.gov.uk/tmcase/Results/4/EU007426265

Normally speaking, to use a protected trademark (in the same usage category as it's registered), you need the permission of the trademark holder.

Ubuntu is slightly different in they want people to use their trademark but they do have rules, as set out in the Intellectual property rights policy (section 3):

• You can use the Trademarks, in accordance with Canonical’s brand guidelines, with Canonical’s permission in writing. If you require a Trademark licence, please contact us (as set out below).

• You will require Canonical’s permission to use: (i) any mark ending with the letters UBUNTU or BUNTU which is sufficiently similar to the Trademarks or any other confusingly similar mark, and (ii) any Trademark in a domain name or URL or for merchandising purposes.

• You cannot use the Trademarks in software titles. If you are producing software for use with or on Ubuntu you may reference Ubuntu, but must avoid: (i) any implication of endorsement, or (ii) any attempt to unfairly or confusingly capitalise on the goodwill of Canonical or Ubuntu.

• You can use the Trademarks in discussion, commentary, criticism or parody, provided that you do not imply endorsement by Canonical.

• You can write articles, create websites, blogs or talk about Ubuntu, provided that it is clear that you are in no way speaking for or on behalf of Canonical and that you do not imply endorsement by Canonical.

Somebody providing a tutorials probably doesn't need to worry. Somebody providing Ubuntu-cobranded tutoring probably does.

IP law isn't an easy (or neccessarily logical) subject. Most of the conventions exist through threat of being civilly sued, not neccessarily because the law prescribes something. If you're using somebody else's trademark and you aren't sure if you're allowed to, you should probably ask them or talk to a real lawyer (not just some guy on the Internet).