To give a straight answer, yes, you can get it as a tattoo as all content is licensed under creative commons. At the bottom of each page you can find the following line:
site design / logo © 2013 stack exchange inc; user contributions licensed under cc-wiki with attribution required
This specific polyglot was a user contribution by Mark Rushakoff in this thread (and therefore falls under the CC portion). The actual design as shown on the 404 page, however, is property of stack exchange inc and cannot be used as-is without permission.
You can read through the lengthy legalese if you'd like, but the general concept is as follows:
You are free:
to Share — to copy, distribute and transmit the work
to Remix — to adapt the work
to make commercial use of the work
Under the following conditions:
Attribution — You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).
Share Alike — If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one.
So you can use the code and diddle around with it as you'd please (or use it as is) and it would not be in violation so long as you properly attribute it to Stack Overflow. In the linked blog post for attribution, the rules are as follows:
So let me clarify what we mean by attribution. If you republish this content, we require that you:
- Visually indicate that the content is from Stack Overflow, Meta Stack Overflow, Server Fault, or Super User in some way. It doesn’t have to be obnoxious; a discreet text blurb is fine.
- Hyperlink directly to the original question on the source site (e.g., https://stackoverflow.com/questions/12345)
- Show the author names for every question and answer
- Hyperlink each author name directly back to their user profile page on the source site (e.g., https://stackoverflow.com/users/12345/username)
So you would need to link to the thread, show the author name (Mark Rushakoff), visually show it came from stack overflow, and link to Mark's user profile.
The tattoo design that you use would also be required to be licensed under the same creative commons (and since everyone loves polyglots, I'm sure it would be all the rage with your friends who would get their own).
This is all without having to ask for permission at all!
Of course, you may get specific permission from Mark Rushkoff (since he owns the material according to the Terms of Service as best as I can understand it as a non-lawyer) to use it without visual attribution or requiring to share the designs under share-alike. You should consult a copyright attorney to figure out how copyright applies to tattoo designs, and to confirm the above to be sure. Or you could just get it done and hope that StackExchange doesn't pursue a lawsuit filled with unicorns for expert witnesses, and many exhibits consisting of freehand circles.
