The Koch Brothers, David and Charles, are the fifth richest people in the United States. They get their revenue from Koch Industries. The Koch’s are philanthropists and also use their vast wealth to promote right wing political organizations including several that they have created. Their political beliefs are Libertarian,  believing in the least amount of government. They are major funders of the Tea Party, thus belying its “grass roots” origins.
Perhaps the reason for their activism is there desire to not have a government that would interfere with their business. Their record shows that they do not want follow the laws that exist and would like to have them rescinded.
They are definitely anti-union. See Tea Party (Koch Brothers) begin push for “Right-to-Work” constitutional amendment for 2012 
Perhaps their goal of reducing government is best exemplified in the following article, which, near the end, points out their role as one of the nations top 10 polluters. They apparently want there capitalism unfettered by any requirement to keep from poisoning the planet.
From a report at the Center for American Progress Action Fund, “The Koch Brothers, What You Need to Know About the Financiers of the Radical Right,”  the following claims are made.
As this report will demonstrate, the Koch brothers’ network works hard to advance a right-wing ideological agenda that helps their businesses reap more profits at the expense of our environment, our economy, and the American middle class. Understanding how they operate is the first step in countering their efforts to reshape our nation’s laws to benefit the wealthy even more than they do today.
One might come to the conclusion that the Koch Brothers are attempting to buy the government of the United States, perhaps the biggest Pay-to-Play political game in the world. It remains to be seen if the American public will allow this to happen.