Koasati...regarding the apparent 'double-standard'....the skinning community sites have a responsibility to respect and protect other skin authors in the community by rejecting rips of their work.
When it comes to artwork derived from OS's, whether Apple or XP, it is the direct responsibility of the Product owners to police. If Apple were to contact skinning sites and demand that ALL OSX-derived works and imagery were removed we would have to comply. When it comes to Microsoft, I really believe that they have seen that it's in their best interest to nurture this use of their product in this way as it only promotes greater interest and therefore profit to themselves.
If person ONE grabs an OS icon and modifies it in some way...and the OS maker does not take issue, then all is well.
If person TWO does the same...well and good.
If however, person TWO takes the work of person ONE and modifies THAT and uploads it..then we have a 'rip' problem, even though both works are essentially the same OS origin.
The problem is that now we have someone within our sphere of control/management that we can protect and oversee...