After having to deal with a ton of issue requests, I am sure GitHub will see the light and change this to a better requirement.
Also, have you heard of Netlify. They will Host it to their Global CDN for free and they are fast as hell. Also can use private repositories on Github also.
The problem is not so much the font weight as the font itself. Time to abandon 'Humbug' on that site which is translating to SourceSansPro-Light-webfont at font-weight: 300.
After having to deal with a ton of issue requests, I am sure GitHub will see the light and change this to a better requirement.
Also, have you heard of Netlify. They will Host it to their Global CDN for free and they are fast as hell. Also can use private repositories on Github also.