SCCT has a new source code repository: https://github.com/SCCT/scct
As a result you can fetch a release version from maven central with addSbtPlugin("com.github.scct" %% "sbt-scct" % "0.2")
in your plugins.sbt file.
My project to reproduce is on GitHub.
Update:
The repository has been relocated at https://github.com/sqality/scct
and you need addSbtPlugin("com.sqality.scct" % "sbt-scct" % "version")
in your plugins.sbt file.