It is an odd clause certainly, since it doesn't forbid anything that isn't already illegal. There is no restriction here that was not already applicable via the same laws that make the APSL (or GPL) enforceable. I'm not sure why Apple felt the need to include that text, but it is not part of the licence: it seems only to be a legal warning to the end-user. If the "free software" fanatics deem these warnings to be "restrictions of use" that render the software "non-free" then we have a rather large problem. Free software isn't about the right to break existing law.
It's no different from saying you cannot use GPL software to illegally reproduce GFDL documentation. (For example, you cannot combine auto-generated documentation from your GPL program with existing GFDL documentation). It is not a restriction -- it is a legal fact that you cannot do that (at least in countries where the GPL and GFDL are legally valid licenses). And it is possible that users will need to be reminded of that fact. But if I include a warning to that effect in my source files, is that an "additional restriction" that renders my code non-free?