This sort of defeats the purpose of the picture.... Doesn't it?

delicious irony

loooool XD XD XD XD XD XD never saw soomething like that ^^

Voted up for sweet sweet irony. And to think this poor artist even bothered writing the message in English...

Was the artist serious when he made this message?

SaphireJack said:
Was the artist serious when he made this message?

Some people are like that. They get seriously offended when someone infringes their intellectual property without the artist's permission/compensation and will go to serious lengths to preserve their works, or at least get credit where credit is due.

tl;dr They're ATTENTION WHORES.

If you look a it in his point of view the picture is not very ironic.
1: As JohnAnon pointed out:

JohnAnon said:
Some people are like that. They get seriously offended when someone infringes their intellectual property without the artist's permission/compensation and will go to serious lengths to preserve their works, or at least get credit where credit is due.

This artist may be afraid that his art will be used and/or abused despite his intentions and/or lose control over them.

2:If you look at his other pictures they are somewhat simple and have no signature. This makes it easy for anyone to use the pictures in and out of context.

3: Therefore the statement in the picture may refer to the other pictures along with itself.