Hi,
I have been able to run this script in LoadUI using the Geb Runner. I believe this might be a problem with how LoadUI is handling @Grab.
What I did was:
- Tried to run the script in LoadUI and, like you, got this exception that @Grab could not download dependencies....
- Ran the script using the
Groovy Console (which is really great to debug). The following is my full test script:
@Grab(group='org.codehaus.geb', module='geb-core', version='latest.release') // this is not required, LoadUI includes a version of Geb already.
@Grab(group='org.seleniumhq.selenium', module='selenium-htmlunit-driver', version='latest.release')
import geb.Browser
Browser.drive {
go "http://05ten.se"
assert $("img").size() == 2
}
- Just try again to run the script in LoadUI. It just worked

Hope this also works for you!
Renato