It’s great to hear from someone working for such an important cause. As an aside, you may be interested in this story written by a camper who goes by @Zersiax: https://medium.freecodecamp.org/looking-back-to-what-started-it-all-731ef5424aec
To your question: contributing to Open Source for Good projects at freeCodeCamp is completely optional. The certificates are earned by building practice projects in the challenges on the Map. In terms of earning “credit” for volunteering your skills and writing code, we’ve got a proof of concept to accurately reflect merged PRs against freeCodeCamp repos on your FCC profile page. This should be implemented sometime this year.
We don’t currently have any Open Source for Good projects tailored toward blindness initiatives, but if you’d like to email me at email@example.com, I’d be interested in learning more about the types of software your organization uses and whether or not an open source solution would save nonprofits in your sector significant funds.