Is the percentage paid to me by the company I recommended to my friend, in exchange for my recommendation, permissible for me, knowing that I am not a broker?

It is permissible for you to accept the amount offered by the company of its own volition, even if you are not a broker. The difference between you and a broker does not lie in the permissibility of accepting the amount, but rather in its obligation upon the company. A broker is entitled to what he has stipulated with the company, whereas you are not. However, if the company gives it to you of its own volition, there is no harm in you accepting it.