I had a lot of traffic generated from my InfoQ post on OSGi in the Enterprise (in which I echoed what everyone else has been saying during my absence) that if you want a kernel capable of modular development (whether dynamic or not), building upon OSGi is both the industry and the de facto standard. Of course, it might be a bit too low level for everyone, which is why systems like SpringSource DM Server are so important; to give people the benefits without forcing them to do things in an unfamiliar way.