I believe I met Bob for the first time in 2007. I was already leading the Apache Groovy project back then (started in 2003) and had the chance to do a "tech talk" at Google, in Mountain View, to present the language to Google engineers.
In the crowd, there were pretty famous people like Guido Van Rossum (of Python fame), Cédric Beust (TestNG), Romain Guy (on Android), Patrick Chanezon... and of course "Crazy" Bob Lee, who was working on Guice and the Android libraries. Very humbling.
I then met him a few times at JavaOne, and maybe some other Java-related conferences or parties! I didn't know him very well though, but I highly respected him. However we had some heated-discussions on programming languages! Bob thought Groovy wouldn't last long, but Groovy is still there 20 years later. He was rooting for BeanShell...
Oh time flies!
It's so sad, so terrible! I often walked those streets myself (the Google office is right around the corner)
Also under the radar because such companies using Groovy sometimes ask us to not speak publicly about the fact they're using Groovy... to my great disappointment!
The static features of Groovy 2.0 are actually a reaction to users demand and wishes.
You can read the article to have a more elaborate explanation of this, but in a nutshell, our users want to be able to type check their code especially when Groovy's used as a kind of "scripted Java" as they expect the same feedback as the java compiler provides. Especially when Groovy is used "à la" Java rather than to rely on its useful dynamic features. And our users are also interested about pure raw speed for computations, or avoid being subject of monkey patching, hence why static compilation matter in some situations.
I don't want to enter into polemical arguments here, as I have nothing against Scala, on the contrary. But your arguments about type systems vs dynamicity or supposed Groovy's drawbacks don't really seem to be factual and backed by any concrete claims or analysis. So I won't comment on that.
The static features were not integrated from the Groovy++ project, as it differed in various ways compared to what we had in mind for Groovy. But Groovy++'s definitely been a great inspiration for us when we developed those features, and the project clearly showed the interest of the community for that.
Unfortunately, I cannot give some of the real-world DSLs that I know of or that I've worked on, as my customers request that we don't publicize that information.
Just to give you a couple examples which are more or less public, I can mention the Amadeus travel company (whose services are used by 80% of airlines and travel agencies in Europe) or the European Patent Office who did presentations at conferences about their usage of Groovy for DSLs.
The various sectors I mentioned earlier are sectors for which I know companies that are using Groovy for such DSL purposes, although I'm not in a position to publicly speak about them unfortunately :-(
As for Gradle, yes, of course, it's used beyond the Groovy ecosystem. For example, the Spring project (and other related Spring projects) is built with Gradle, as well as Hibernate. Some major projects have switched to Gradle from Maven.
No, Groovy is used in many other places than Grails.
One can think of the Gradle build automation tool (http://gradle.org/), for instance, which uses Groovy as a DSL.
But actually, one of the very big use cases for Groovy outside of Grails is as an embedded DSL, for business-oriented languages, to further customize the business rules of an application, for configuring it, etc.
Groovy's used in many sectors: healthcare, insurance, banking, travel, scientific simulations, biomedical, etc.