Both the back end blockchain service (steemd) and the front end (condenser) are MIT licensed. However, the licensing of the software used is not relevant in terms of content posted. Steemit's legal jurisdiction is in the US and as such is subject to copyright infringement claims, aka DMCA takedown requests. We can't modify what gets posted to the blockchain but can be legally abliged to filter content that gets displayed from the front end web site. This is not censorship, it's just law within the jurisdiction that the front end website is hosted.