It would need to be clearly labelled as documentation for 0.7.x versions only, and should retain links to the newer documentation, IMO. (Although since github docs have largely moved to scala-sbt.org, these should generally point to elsewhere on scala-sbt.org rather than the github wiki as they do now.)
IMPORTANT This project has moved to https://github.com/sbt/sbt. This issue still exists to avoid dead links, but GitHub limitations prevent the original issue from being correctly preserved here. Please see sbt/sbt#568 for the full issue and to comment.