This is the opening paragraph on the ABOUT page of the protectourelections dot org website.The claim in the last sentence does not appear to be true.
The IRS publishes a list of all registered 501(c)(3) organizations. Protect Our Elections is not on the current list (updated on 8 October, 2018) under its current name, its previous name (Velvet Revolution US), or its Employer Identification Number.
Further, it appears from the information posted on the IRS website that it is not possible for a 501(c)(3) organization to be simultaneously registered as any other type of Section 501 entity.
Protect Our Elections/EMPR Inc. does appear to be registered with the IRS as a 501(c)(4) organization. For now. Kimberlin’s other not-for-profit, Justice Through Music Project, is registered under 501(c)(3). However, they are two separate entities, and commingling their assets could … never mind … I’ll let him find out the hard way.