“Steem,” “ Streemian,” the Streemian logo and any other product or service names, logos or slogans that may appear on Streemian are trademarks of Streemian and may not be copied, imitated or used, in whole or in part, without our prior written permission.
Quote from https://streemian.com/terms
As per their T&C to use Steem and Steem logo on your app/product you should get written permission from them.
How and why they claim we should ask them for premission to use 'Steem' term.
On their site is also displayed Steem logo which is their own per T&C.