The Supreme Court has a whole protocol for this: http://www.supremecourt.gov/opinions/slipopinions.aspx ("Caution: These electronic opinions may contain computer-generated errors or other deviations from the official printed slip opinion pamphlets. Moreover, a slip opinion is replaced within a few months by a paginated version of the case in the preliminary print, and--one year after the issuance of that print--by the final version of the case in a U. S. Reports bound volume. In case of discrepancies between the print and electronic versions of a slip opinion, the print version controls. In case of discrepancies between the slip opinion and any later official version of the opinion, the later version controls.")
The GigaOm article is garbage: "Supreme Court opinions are the law of the land, and so it’s a problem when the Justices change the words of the decisions without telling anyone." They're trying to generate page-views by making it sound like the Justices are going back and changing the official record, and are being thwarted by a coder who swoops in to save the day.
In reality, what you have is a tool to see what changes between the "release candidate" and the "Gold Master." Still interesting, even without the manufactured drama.