The SigTest upstream project doesn't provide binaries of SigTest any longer and also won't publish this Maven plug-in it seems. There is a plug-in provided by the NetBeans team which we are using now. This contains a fork of the upstream code base, so it'd still be desirable to move back to the upstream one eventually, as it's being worked on actively for Java 9, amongst other things.

The change has been integrated, but leaving this issue open for the time being as the docs still need some love.