In the beginning God created Ruby. Ruby came with many new possibilities, but was without a good web application framework. God said "there should be Rails" and Rails came into existence.
On the second day came a lot of fuss about Rails.
On the third day Grails was born.
Grails follows the Rails way of "coding by convention", using Groovy, an agile dynamic language for Java. Grails is 15% made of Groovy (the rest being Java) while Rails is 100% Ruby, hence Grails can not be properly called Groovy on Rails. Starting from that simple observation, Charles Nutter, one of the JRuby developer from Sun wonders how Grails could be extended to support any scripting language, especially Ruby.
I decided to do this exploration after realizing there's nothing about Ruby or JRuby that couldn't be used to wire a bunch of Java libraries together--indeed, that's one of the biggest selling points of JRuby, the fact that you can write plain old Ruby code but call Java libraries almost seamlessly (with day-by-day improving integration points and performance numbers). So why not take Grails and do a port to Ruby? Groovy code isn't far off from Ruby in many ways, and everything you can do in Groovy you can do in Ruby (plus more), so the port should be pretty straightforward, right?
Charles wants the best of both worlds: Multi-Language ability with the rich support of existing Java libraries. Graeme seems to be eager to stay in the "Java-Land".
In a straightforward answer, Grails founder Graeme Rocher after making advertising for his framework, tends to answer that the support of other language in Grails is just a matter of available resources, and harshly criticizes Sun's investment in "dead-end projects" such as Phobos.
The quarrel eclipses a major root question: Do we turn the page and move from a 100% Java world to 100% Ruby ? Charles (Sun) and Graeme don't want that and bring their own solution.
Now why not just use the 100% Ruby On Rails solution, and constantly build new Ruby libraries around it while the performance (something it is being criticized for today) is being improved? Can the standalone Ruby and Rails couple survive Sun's orientation? The IT world will make its choice in the near future.