Can the Java Metro stack be used in commercial closed source projects?

Question

After some more research I found that the Netbeans framework is licensed with the same construct (GPLv2 and CDDL) and luckily the guys at Netbeans took the time to explain the how what and why a bit:

Netbeans license FAQ

Here is what they say about dual-licensing:

Dual-licensing is the practice of distributing identical software under two (or more) different sets of terms and conditions. When software is dual-licensed, recipients can choose which terms under which they want to obtain the software. The two usual motivations for dual-licensing are business models and license compatibility. [...]

Additional search for details about CDDL brought me to this site containing a nice summary:

why the dislike for cddl

Here is one of the parts relevant that is to my question:

CDDL is a file-based license. This means that if you make any changes to CDDL-licensed software, any existing files that you modify need to remain under CDDL, but any new files that you create can be under whatever license you want as long as that license isn't incompatible with CDDL.

Conclusion (note that I'm not a lawyer and this is no legal advice - just my personal interpretation based on the available information):

Metro seems to be useable for commercial closed source projects but changes to the existing source have to be made available under the same license as the original source.
So as long as one is just using the libraries the own source code can be kept completely closed source.
At least if CDDL is chosen.