Vedic knowledge must be transmitted 'as it is' received from the original source. For us the literature is the Bhaktivedanta literature and that is originally received from Lord Sri Krsna all the way to Srila Prabhupada.
In fact, to teach us this principle Srila Prabhupada even named the exposition of Bhagavad-gita as Bhagavad-gita as it is. It denotes the parampara where nothing is added or subtracted from the previous acarya.
Besides this is there any other principle to be followed?