Facebook founder Mark Zuckerberg and his wife Priscilla Chan's recently announced $45 billion philanthropic pledge will be given away not through a nonprofit foundation but instead through a for-profit company the couple is creating.

They've donated to health care and education in the past, but this time it appears they'll be giving away billions of dollars through a limited liability company, known as a LLC. The for-profit company is called the Chan Zuckerberg Initiative.

"He's giving himself a huge amount of freedom. He and his wife are a very young couple, and they're giving themselves the freedom to decide what will be the most effective way of dealing with the social issues they care about," says Paul Brest, a professor at Stanford and former president of the William and Flora Hewlett Foundation.

Brest says one big difference between a nonprofit and a private company is politics.

"A foundation itself is not allowed to do what the Internal Revenue Code defines as lobbying," he says. "If you're trying to achieve a social end through advocacy, you're going to find yourself very constrained, whereas if you're just paying it out of your own pocket if you're a company or an LLC, there are really no constraints at all, at least imposed by the tax code."

In a public letter to their newborn daughter, Chan and Zuckerberg said about their philanthropic goals, "We must participate in policy and advocacy to shape debates."

Mollie Cullinane, who runs a law firm that specializes in philanthropic giving, says creating an LLC instead of a nonprofit looks like a move by Chan and Zuckerberg "to get more deeply involved in advocacy and promotion of certain causes that other charities and foundations can't speak out about as loudly."

Zuckerberg doesn't fit into an easy political definition. He and Chan support clean energy and solving climate change and have taken a more liberal stance on immigration reform. At the same time, Zuckerberg has donated money to both Democrats and Republicans, including Marco Rubio.

But beyond politics, there are other ways an LLC will give the couple philanthropic flexibility.

"There's a whole new area opening up, so-called impact investing, where you invest in a for-profit organization that has a social mission," Brest says.

So the couple might invest in clean energy companies, for example, and could make money off those investments. Foundations can do some of that. But, Brest says, "you are freer from any restrictions if you simply do it through a private company."

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