You are refering to Widget SDK - http://www.betavine.net/bvportal/resources/widgets/research
That is mainly a "Packager", that will help you to create a widget (either from scratch or based on two tutorial widgets), it also comes with the Opera Desktop and a s60 developer binary (that is enabled to do remote debugging)
The JIL SDK comes with an eclipse IDE, and an emulator.
The emulator can only run jil widgets, and the sdk is more in a beta stage.
Therefore I recomend using the packager for building widgets, and at least have a look at the jil-sdk and provide feedback.
Hope that helps.
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Jochen