Why is the Declaration of Independence still applicable today?

The Declaration of Independence is still applicable today in that it states who should be in charge of the American government—the American people. It says the government derives its power "from the consent of the governed." It also states the government is necessary to provide for the people's "inalienable rights," which according to Jefferson are life, liberty, and the pursuit of happiness. The rhetoric in the Declaration of Independence has been used by American politicians as well as leaders in other countries who wish to create their own forms of self-government.  
The Declaration of Independence is also important in that it gives a list of wrongs committed by Britain against the American colonies. Without this list, the American colonists are only tax-dodgers. This list shows the colonists have legitimate complaints.  
Finally, the Declaration of Independence gives the American people a right to revolution.  A passage states "the people have the right to alter or to abolish that government, and to establish a new government," which means that if the government infringes on life, liberty, and/ or the pursuit of happiness, people have an inalienable right to change the government or establish a new one. The next passage begins with the word "prudence," however, meaning the people should take this responsibility seriously and not flippantly alter the government on a whim.  
http://www.let.rug.nl/usa/documents/1776-1785/the-final-text-of-the-declaration-of-independence-july-4-1776.php