At the moment, STS places a red underline under the import statement in the following Groovy script:

Code:
@Grab(group = "net.sf.delicious-java", module = "delicious", version = "1.14")
import del.icio.us.Delicious

// rest of the script
Ideally STS should inspect the contents of the net.sf.delicious-java:delicious:1.14 module and then recognize and resolve del.icio.us.Delicious as a valid class name.