As far as I understand, they (the W3C) do this every few months in an attempt to wrest defacto control of HTML back from WHATWG. They copy the WHATWG spec, strip out the licensing and authorship information, and publish as "their" HTML spec.
Then a few months passes, their copy falls behind the actively edited WHATWG one, so they have to fork it again. And so on, and so on.
That's a really interesting look at the politics between those two. Applies to some stuff I'm involved in too. Useful link, thanks very much for sharing!
The W3C prefer their specifications to be 'finished' at a certain point, and the WHATWG simply add their changes to the living spec.
So for the most part, changes get made in the WHATWG spec, they get copied to the W3C one, the W3C then stops copying additions at a certain point (say, when HTML 5.0 is considered 'complete') and then moves onto version 5.1. So version 5.1 is basically all the WHATWG additions that didn't make it into 5.0 before the spec was 'finalised', along with various changes made because the two groups don't get along with each other too well.
As far as I understand, they (the W3C) do this every few months in an attempt to wrest defacto control of HTML back from WHATWG. They copy the WHATWG spec, strip out the licensing and authorship information, and publish as "their" HTML spec.
Then a few months passes, their copy falls behind the actively edited WHATWG one, so they have to fork it again. And so on, and so on.
It's really pretty pathetic.