I don't know the details, but here is what the IRS says about it. Looking at it, I don't know how they could have qualified for 501(c)3 status in the first place!
Exemption Requirements
http://www.irs.gov/charities/charitable/article/0,,id=96099,00.html
To be tax-exempt as an organization described in IRC Section 501(c)(3) of the Code, an organization must be organized and operated exclusively for one or more of the purposes set forth in IRC Section 501(c)(3) and none of the earnings of the organization may inure to any private shareholder or individual. In addition, it may not attempt to influence legislation as a substantial part of its activities and it may not participate at all in campaign activity for or against political candidates.
The organizations described in IRC Section 501(c)(3) are commonly referred to under the general heading of "charitable organizations." Organizations described in IRC Section 501(c)(3), other than testing for public safety organizations, are eligible to receive tax-deductible contributions in accordance with IRC Section 170.
The exempt purposes set forth in IRC Section 501(c)(3) are charitable, religious, educational, scientific, literary, testing for public safety, fostering national or international amateur sports competition, and the prevention of cruelty to children or animals. The term charitable is used in its generally accepted legal sense and includes relief of the poor, the distressed, or the underprivileged; advancement of religion; advancement of education or science; erection or maintenance of public buildings, monuments, or works; lessening the burdens of government; lessening of neighborhood tensions; elimination of prejudice and discrimination; defense of human and civil rights secured by law; and combating community deterioration and juvenile delinquency.
Political and Lobbying Activities
(Adapted from IRS Publication 1828, Tax Guide for Churches and Religious Organizations - February 2004)
http://www.irs.gov/charities/charitable/article/0,,id=120703,00.html
I've saved your info so I can really research what it says tomorrow - but right off the bat - I saw this statment: "it may not attempt to influence legislation as a substantial part of its activities and it may not participate at all in campaign activity for or against political candidates."
"influence legislation" - may not relate to impeachment - but the Articles of Impeachment might be considered legislation - I don't know.
What with tax season upon us - the IRS will be very busy - but I don't want to wait. I'll have to think about it.