yes, if apple blocked websites that would be censorship, because they don't own the world wide web. if they block an app from appearing in their store that's a private company deciding not to have something in their product. that's not censorship.
by your logic, everything on the internet practices some sort of censorship. like i said, droidforums has a language filter, deletes posts that they find offensive, and bans people that troll. are they practicing censorship?
Blocking websites vs. apps that deliver content is a distinction without a difference.
And, YES!, filtering language is a form of censorship. It's practically the definition. What do they say on tv when stuff gets bleeped or deleted - "didn't make it past the censors". Not all forms of censorship are bad or harmful and some actually have merit, but it is censorship nonetheless.
MS is not a great example because it was dealing with anti-competitive behavior and they did not block Netscape just didn't preload it while they did with IE - they were using a dominant market position to favor their own product, so bad example on my part. But as I said, it's not entirely dissimilar. By your logic, MS was fully within their right to favor their own product and making it difficult to choose an alternative and that was illegal.
Droidforums is not a form of censorship in providing targeted content. Many other websites have "off-topic" forums where virtually everything under the sun is free to be discussed. Apple's app store is really pretty similar - the guidelines are basically no porn and no malicious software but that's pretty much it. They made an exception that singled out this particular app and it's a clear form of censorship. Like I said, it's pretty trivial and immaterial, but it's censorship no matter how you spin it.
How do you feel about web neutrality? When you have apps designed to deliver content in a more accessible and user-friendly manner, it really becomes an extension of the web and censoring apps is part and parcel the same as censoring the web.