This is curious. I thought George Mason Univ was a conservative (at least by today's standards) outfit.
Did some graduate assistant doctor the original before posting on the GMU website?
I had not read the complete version for a while and thought something was missing.
Where did you find the version you posted?
I Googled "White Man's Burden" and found a version where three websites agreed.
I cannot profess an academic knowledge of Kipling, but that couplet made a lasting impression upon me when I first read it, which is why I noticed it was missing. Going back and reading the GMU version, one can see that all the negative language of the poem has been removed, which changes the tone of the poem from a precautionary tale to a pep rally.