A non fee paying portfolio is managed on a PRO BONO basis?

In the Kaplan note, it states that “an example of a non-fee-paying portfolio is one that is managed on a PRO BONO basis.”

At first, I thought non-fee-paying portfolios are charged with commission and transaction fee. How come it becomes free now?

Thanks!

Probably means no management fees. Transaction fees and commissions are paid to brokers.

That makes sense! Thanks!