Ultimately, you can post any content you like into the steem blockchain, and nobody from steemit has any say about it.

By default, we publish all of those posts onto the site (unless you have low reputation). If you publish something that a government can force us to remove (and they do), we will have to hide it on steemit.com, but it will always remain in the blockchain, visible to the entire world. We can't control that part, because it's a peer-to-peer network and while we can be forced to hide it on our steemit.com site, the content will remain public on other sites that display information from the same blockchain. Today there are 5-7 such sites, and I expect there to be more in the future.