Several plugins in the NetBeans Plugin Portal
can be used in applications other than
NetBeans IDE. Sure, many of them relate to editor functionality, hence those would probably apply mainly/only to NetBeans IDE. Others, however, could be used in any other application that is based on the NetBeans Platform. Here, for example, is the YouTube Player from the Plugin Portal installed in the JFugue Music NotePad
So, if you're creating applications on top of the NetBeans Platform, I advise you to have a look at the Plugin Portal from that perspective, i.e., not from the perspective of NetBeans IDE, but from the perspective of your own application. Who knows, maybe you could even come out with a whole new release with features provided by plugins that you've grabbed from the Plugin Portal...