The whole point of level playing field is that they must be remunerated, so there is no instance of someone doing something for free.

We had similar problem in my country with apprenticeships, that used to be unpaid. The good ones where snapped up white middle class children, while children from ethnic minorities had to work for money, not necessarily in their field of interest. That amplified the lack of diversity in the space of white collar jobs. Now unpaid apprenticeships are illegal and that has vastly improved the access to jobs for people from disadvantaged backgrounds.

It's exactly the same situation with OSS.