Both Grails and Gradle ship with the Groovy Language, and are its main two products by number of users - if they disappeared, Groovy's only use of any significance would be short scripts manipulating and testing Java classes. (Though I'm not sure if I'd describe Gradle build scripts as "using" Groovy, more like 50 lines using a tiny subset of Groovy's grammar and functionality.)

And of course Grails is promoted by VMWare and Gradle by GradleWare. There's no info about GradleWare's true owners in the verbiage on their about page. Either they want to be bought by VMWare, or they were started with seed money from them and effectively controlled by them.