This is correct. However, I think it is good practice to properly attribute trademarks in those cases to make sure that it is clear that it is intended in this

This is correct. However, I think it is good practice to properly attribute trademarks in those cases to make sure that it is clear that it is intended in this way. A small disclaimer at the bottom of the page saying: Tumblr(R) is a registered trademark of Tumblr, Inc. which is not affiliated with this site. All other trademarks are owned by their respective owners. goes a long ways towards avoiding problems like this.