I have been a long time user of NetBeans IDE. I really like the simplicity and how it is almost an all-purpose IDE for virtually any language you can think of.
However, I was horrified recently when I upgraded to version 6.8, to discover that the UML module was gone, and instead NetBeans insisting I use a third-party UML generator. So I tried it, and hated it immediately. I considered rolling back to an earlier version, but first I thought I would try a little voodoo.
I noticed that version 6.9 was released and so I downloaded it, and installed as per normal. I then found this page (the 6.9 release candidate zip download page) which listed a file called ‘netbeans-6.9-201005312001-ml-uml.zip’. Ah ha. Since I am on OSX, I opened the package contents up from Applications, unzipped the uml.zip file and dropped the new UML directory into the installation directory. I started up NetBeans and voila:
I tested the new project, and it worked like a treat (some people who tried various other hacks reported that even though the project appeared, there was issues saving/opening them).
I hope this works for you too, and of course make sure you backup any existing projects – dont come crying to me if you destroy your work trying to implement this!