The Rocket.Chat logo and wordmark artwork are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Under fair use of US trademark law a nonowner may use a trademark nominatively—to refer to the actual trademarked product or its source.
So if you want to use the word Rocket.Chat to refer the product or source that is distributed on https://rocket.chat/ that is OK, no need to ask us for permission.