JSPM is making some major breaking changes in their 0.17.x release. We have attempted to update Aurelia's package.json files so that Aurelia could be installed with either 0.16.x or 0.17.x. We spoke with Guy from the JSPM team extensively about this so that we could do it right. However, there were a number of things Guy didn't expect and things didn't go as smoothly as we wanted. As of now, we do support 0.16.x with some restrictions which we've outlined in today's blog post. We are working with Guy to finish the last changes needed to support 0.17.
This isn't the first time this has happened to us. So, I confess, I'm not very happy with the situation. We will continue to support jspm/system.js, but post v1 we are also going to be investigating our own solution. We'd like to support as many package managers, loaders and bundlers as possible. However, our recent experience has led me at least to believe that we may be able to build something much simpler and more stable ourselves which could become the default in the future (without cutting out anything we already support today.)