e source  code, which must be distributed under the terms of Sections 1 and 2  above on a medium customarily used for software interchange; or,</blockquote>
<blockquote>b)  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 