Eric Welch says, "Leonard Peikoff, who has declared Objectivism to be a 'closed' philosophy, i.e., no critical analysis will be tolerated; one must accept it as he says it is and that's that."
As I understand it, Peikoff thinks that what ought to be called "Objectivism" is simply what Ayn Rand published and what her associates published with her editorial oversight. Since Rand is dead, that means Objectivism, BY THIS DEFINITION, is necessarily and obviously "closed". Needless to say, a great many people who have been influenced by Rand's philosophy think their own take on Objectivism to be part of Objectivism too, just as new works by devotees of Freud may be thought, especially by their authors, to be part of Freudianism. I think Peikoff may be fighting a loosing battle for his preferred definition but you will understand that there is considerable merit to it if you are familiar with the extremes of distortion to which Rand's Objectivism has been subjected by both her detractors and purported admirers.
The business about how "no critical analysis will be tolerated" is false, as anyone who visits the website of Peikoff and his associates at the Ayn Rand Institute can see. It is loaded with all kinds of critical analysis, most of which was not authorized by Rand, of course, and not all of which would be endorsed by Peikoff, since no two people will see everything exactly the same, even if they share an explicit philosophy. If you mean that no critical analysis by detractors of Ayn Rand is tolerated by Peikoff and associates, that is true, but that is no more than one expects from such an institution: it is devoted to the PROMOTION of Objectivism. Many of Peikoff's associates are members of the Ayn Rand Society of the American Philosophical Society however, and both philosophical detractors and promoters of Objectivism are heard from at their conferences, because that is a neutral, scholarly forum. For example the December 2007 program will be on "The Foundations of Ethics: Objectivism and Analytic Philosophy". You can be sure that the perspective from analytic philosophy will not be supressed in that forum.