ellenmillion has posted a detailed description of
how credits work over on
torn_world. This is a really cool crowdfunding feature that turns subscription dollars into a local currency that you can use to reward contributors whose work you admire. Lots of us will release material to the public if it gets sponsored (via credits or PayPal donation, etc.) so then more people can see it.
ellenmillion is also thinking about ways to make credits work across multiple projects that she manages, which would be even more useful. So get involved, this is where the rubber meets the road.