b) Also Jython is virtually dormant, at some older version of Python, while both JRuby and IronRuby are actively worked on.
c) Groovy hasn't added any support for invokedynamic or even started on it. A month ago they announced they're removing their meta-object protocol rework from the upcoming version 2.0.
SpringSource seem to be repositioning Groovy as a staticly-typed language, this year adding primitive types like in Java. Before everything was an object, and primitives were regarded as leaky abstractions. 2 months ago they employed someone to write a static type checker called "Grumpy" for Groovy, and eventually type inference and optimization, but the work's just started so it might take quite some time depending on how good their new hire is. This year they also tried to rewrite the Antlr 2.7 based parser in Antlr 3.2, using a Google Summer of Code worker, but they didn't get very far. Perhaps the static type checking for Groovy will be more successful, perhaps not.
I imagine this repositioning was instigated by the Grails team wanting a faster language, with dynamicity an optional extra to be used only when required.