All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad
is His slave and Messenger.
Depositing money into a financial brokerage account that is guaranteed and returned to its owner whenever he wants it or after a specified period, is considered a loan. Thus, whatever the owner receives in return for this deposit is regarded as interest (riba). Therefore, this transaction and promoting it are prohibited. What the account holder receives as what you called a “bonus” is not permissible, and likewise, what the person who referred others to the account receives is also not permissible, because it is compensation for a prohibited benefit, and it is considered as facilitating riba.
Allah knows best.