Expression is being released under the Q Public License an Open Source Licensing agreement, and a more traditional commercial licensing agreement.
The software may be used in a software package as long as the conditions of the QPL are met. One of the more notable conditions of the QPL. Is that when modifications to the Software are released under this license, a non-exclusive royalty-free right is granted to the initial developer of the Software to distribute your modification in future versions of the Software provided such versions remain available under these terms in addition to any other license(s) of the initial developer.
If you use the software I'd love to know about it.
A commercial license without the restrictions of the QPL is also available. Feel free to contact me if you are interested in it.