OSGi is, today, one of those trendy acronyms that no longer stands for anything. It's just OSGi.
OSGi did start in the embedded Java space, but if you write any plug-ins for the Eclipse development environment, then you're writing OSGi bundles as Eclipse is built upon OSGi.
All of the Java application servers are now talking about OSGi, with many of them using it under the hood in their latest versions.
As a server-side Java developer (myself and my team are using it), I see OSGi in the early stages of adoption with more developers talking about it rather than using it. Only time will tell if it will become mainstream for Java.