According to my knowlege it makes no difference if the person is being photographed or illustrated - in any case you have the to ask a person for permission for certain types of publishing(not just celebrities)

Any issues on this to do with photographing people are not covered by copyright law.

As I say, "there may be other issues in some countries such as model rights", but this isn't copyright law. The point I was making is that the laws on model rights, or how one random application store decides to enforce them, doesn't tell us specifically about how things might work for copyright law.

Also when you say "the person" being illustrated. In your example, we're not talking about an illustration of a real person, but also that you are copying a fictional character, which is where the copyright problems come in.

I'm not sure if i got this right now:
Are you saying that illustrating a celebrity(und using it in an app ofc) is not as "dangerouse" as illustrating a fictional character, because model-rights are less "strict" than copyrights?
or
Are you saying that model-rights and copyrights are just to different things?

Tom Sloper's FAQ states this issue with the following: '[font=Georgia][size=2]Just as bad. Celebrities make a living from their faces, and they'll sic their lawyers on you real quick if you try that. Celebrities are not fair game like public figures are.'[/font]
So that sounds to me like is doesn't matter in this case if there are copyrights or modelrights involved, one can get trouble from either end, if doing so.
So it's either "getting into trouble for violating some rights" OR "getting into trouble for violating some other rights" ...

So it's either "getting into trouble for violating some rights" OR "getting into trouble for violating some other rights" ...

Or how about "getting a lawyer's advice before deciding how much trouble I'm willing to get myself into." None of the advice you've gotten here is from a lawyer.

Or how about "getting a lawyer's advice before deciding how much trouble I'm willing to get myself into." None of the advice you've gotten here is from a lawyer.

Sure that would be the best solution, but I don't have the money to ask a lawyer these kind of questions, if I had, I would not have to do this kind of research online ony my own :-)
But I probably won't be using other characters and celebs now.

I'm not sure if i got this right now:
Are you saying that illustrating a celebrity(und using it in an app ofc) is not as "dangerouse" as illustrating a fictional character, because model-rights are less "strict" than copyrights?
or
Are you saying that model-rights and copyrights are just to different things?

I'm saying they're different things. I'm also saying that one random app store might treat one different to the other. Or maybe it's just pot luck what slipped through the review system that day. I wouldn't endorse doing either.