That is fine, and there is no need for it. That wouldn't be viable anyway (except for node.js and projects of similar size).

The foundation pays someone else (their contractor) to fix a bug in the OSS project and to make a pull request to the project maintainer. This way the bugs get fixed, enterprise have their support and contractor gets paid. Maintainer of the project also gets something - fixes of his code by seasoned professionals, paid to do their work.