I think the the Netscape Directory codebase took longer than that to fully open..but that was much more than a protocal definition. That directory codebase release had to be staged, the gui admin tools came later because they essentially had to be written and couldn't be opened.
Advanced Message Queuing Protocol isn't a good example either because it was a from the ground up specification that Red Hat has been working on with partners.
The closest previous example maybe when Red Hat purchased Sistina in 2003 and then subsequently open sourced their GFS implementation about a year later. I wouldn't expect it to be faster than how long it took to get GFS opened.
But it really comes down to what the legal particulars of the codebase in question.
Of course none of that historical comparison should keep anyone from prodding Red Hat to do it as fast as possible.