check this page:
Where it says:
"The reference designs for arduino are distributed under a Creative Commons license Attribution-ShareAlike 2.5"
I am not an expert, but the way I read that license is that you can produce anything you want from the reference designs, and sell them for as much as you want. Two conditions come with that permission:
- you have to credit the original Arduino design;
- you have to put the same license on whatever you make with the original designs. So in theory, every successive thing made from the Arduino project is completely open, as it has to maintain the "Attribution-ShareAlike" license described above.
But the part that is missing from the pure copyright approach is that much of the success of the Arduino project is due to the fact that the current manufacturer and the developer have taken big risks to get these boards produced. If you start trying to undercut their prices, it could ultimately do a disservice to the Arduino community, as they may not be able to continue researching and producing such great quality boards in the face of price competition. You have to realize that the 32 USD board represents a design, high-quality manufacturing and most importantly, thousands of hours of development time. If you try to sell just the board without the investment in the project and the development time, well we're back at square one then :)
Just my 2 cents.