This is just a warning, it should build, and can safely be ignored. The error message does indicate that the build system correctly chose v1.0.0.0.
"ServiceStack.Interfaces, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" was chosen
The version was intentionally reset from 3.9 to 1.0, about 4 months ago in this commit. This coincides with the beta release of ServiceStack v4. Presumably the v3 assembly versions where reset to a low number to allow for future BSD builds to be created without encroaching on the v4 version numbering, and to denote the clear change of project ownership.