Charge for shipping..
Yes you can charge for shipping, but it specifically states;
"for a charge no more than your cost of physically performing source distribution"
Taken from the following (Section 3 paragraph "a")
"Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,"
This should effectively keep the shipping cost from becoming a profit-centre.