OptinMonster provides two simple steps to remove/ disable the branding from it's optin.
Step 1. Create/ modify an optin:
Create a new optin or modify an existing one from the OptinMonster Dashboard. Open the OptinMonster Builder by selecting the Edit link.
Step 2. Configuration:
Select the Configuration tab on the left side of the page.
Step 3: Uncheck
Then uncheck the Show Powered By Link? option. Save the optin, and the ‘Powered by OptinMonster link' is disabled.