The problem seems to be caused by a 308 Permanent Redirection from grailsCentral:

| Error Resolve error obtaining dependencies: Failed to read artifact descriptor for javax.servlet:javax.servlet-api:jar:3.0.1
org.eclipse.aether.resolution.ArtifactDescriptorException: Failed to read artifact descriptor for javax.servlet:javax.servlet-api:jar:3.0.1
Caused by: org.apache.maven.model.resolution.UnresolvableModelException: Could not transfer artifact net.java:jvnet-parent:pom:1 from/to grailsCentral (<http://repo.grails.org/grails/plugins>): Permanent Redirect (308)
Caused by: org.eclipse.aether.resolution.ArtifactResolutionException: Could not transfer artifact net.java:jvnet-parent:pom:1 from/to grailsCentral (<http://repo.grails.org/grails/plugins>): Permanent Redirect (308)
Caused by: org.eclipse.aether.transfer.ArtifactTransferException: Could not transfer artifact net.java:jvnet-parent:pom:1 from/to grailsCentral (<http://repo.grails.org/grails/plugins>): Permanent Redirect (308)
Caused by: org.apache.http.client.HttpResponseException: Permanent Redirect (308)

grailsCentral

was decommissioned long ago. You will be lucky if you can find plugins for Grails 2.x anywhere. Time to upgrade!

Thanks - definitely time to upgrade, but my first step was to try and rebuild it!