In lieu of the tax imposed by section 4940, there is hereby imposed for each taxable year on the gross investment income (within the meaning of section 4940(c)(2)) derived from sources within the United States (within the meaning of section 861) by every foreign organization which is a private foundation for the taxable year a tax equal to 4 percent of such income.
Section 507 (relating to termination of private foundation status), section 508 (relating to special rules with respect to section 501(c)(3) organizations), and this chapter (other than this section) shall not apply to any foreign organization which has received substantially all of its support (other than gross investment income) from sources outside the United States.
A foreign organization described in subsection (b) shall not be exempt from taxation under section 501(a) if it has engaged in a prohibited transaction after December 31, 1969.
For purposes of this subsection, the term “prohibited transaction” means any act or failure to act (other than with respect to section 4942(e)) which would subject a foreign organization described in subsection (b), or a disqualified person (as defined in section 4946) with respect thereto, to liability for a penalty under section 6684 or a tax under section 507 if such foreign organization were a domestic organization.