I've looked around, and I'm surprised that I can't find an Open Source equivalent to Oxygen or XMLSpy. i.e. A rich XML editor with support for diverse types of validation, XSLT debugging and profiling, and all the other extra bits that make it more than just a text editor with syntax highlighting.
I've seen a few (like Jaxe), that that offer different ways to edit xml documents, but nothing that rolls it all up into an IDE-like application.
I'm sure this means I've missed some very worthy project. Can anyone point me towards such a thing?
[Addendum]
Although it's interesting to hear about free licences for proprietary software, my question is really about Open Source Applications.
Background: I normally maintain that when looking for software for software development, OSS is the first port of call, as developers quite like "eating their own dog food". Normally, one needs a compelling reason to look at proprietary software in this domain. This seems not to be the case regarding XML Editors, and that surprised me.