I found this today on Microsoft's site.
Source: http://msdn.microsoft.com/directx/XNA/faq/default.aspx
This last bit sounds promising
Q: What if I have an 360 Developer Kit – can I use the XNA Framework with a title that I intend to send through certification?
A: We will be releasing XNA Game Studio Professional next spring which will support the creation of commercial games on the Xbox 360 using an Xbox 360 developer kit. Titles created with XNA Game Studio Professional by developers with approved titles will be able to be submitted for certification, unlike games made using XNA Game Studio Express.
(NEW) Q: What is XNA Game Studio Express?
A: XNA Game Studio Express is a new offering, targeted at students and hobbyists for game development. XNA Game Studio Express is based on Visual C# Express 2005 and lets developers target both Windows and Xbox 360. XNA Game Studio Express contains the following:
The XNA Framework, a set of managed code development libraries that make it possible for game developers to be more productive when creating games for Windows and the Xbox 360.
The XNA Framework Content Pipeline, which is a set of tools that allow developers to more easily incorporate 3D content into their games.
XNA Game Studio Express also contains a full set of documentation, how-tos, and starter kits that demonstrate how best to use the content pipeline and XNA Framework.
The beta of XNA Game Studio Express has now been released, and can be found here. It currently supports Windows game development only.
(NEW) Q: Are there any prerequisites to run XNA Game Studio Express?
A: Yes, you must download and install Visual C# Express and the latest DirectX runtime updates. If you wish to modify/created audio files, you must download the full August 2006 DirectX SDK in order to use the XACT audio tool.
Q: How much will XNA Game Studio Express/XNA Framework cost?
A: The XNA Game Studio Express tools and runtime environment for Windows is completely free. To develop, debug and/or play games on the Xbox 360 you will be required to purchase a XNA “Creator’s Club” subscription on the Xbox 360 through Xbox Live Marketplace. The subscription is available in 2 options, $99 a year or $49 for 4 months.
Q: What exactly is the XNA Framework?
A: The XNA Framework allows game developers to create modern games using the C# programming language and a rich set of development libraries. The XNA Framework provides its own content pipeline to make it easy to get rich content (3D, 2D, sound, etc.) from content creation sources into a game. The XNA Framework also provides a very high level of API unification across the Windows and 360 implementations, thus virtually eliminating the cost and effort required to port games between these two platforms.
Q: How exactly can I share my 360 game to other 360 users? Will my game only be available to people with the XNA “Creators Club” subscription? Will it be available to all 360 users that have an Xbox Live account?
A: There is currently no supported way to share binaries on the Xbox 360. Currently, there are four requirements that must be met in order to share a game targeting Xbox 360 which is developed with XNA Game Studio Express.
The individual you are planning to share the game with must be logged in to Xbox Live and have an active subscription to the XNA Creators Club
The receiving user must have downloaded the XNA Framework runtime environment for the Xbox 360
The receiving user must have XNA Game Studio Express installed on their own development PC
The game project, including all source and content assets, must be shared with the receiving user. The receiving user then compiles and deploys the game to their Xbox 360.
Source: http://msdn.microsoft.com/directx/XNA/faq/default.aspx
This last bit sounds promising
Q: What if I have an 360 Developer Kit – can I use the XNA Framework with a title that I intend to send through certification?
A: We will be releasing XNA Game Studio Professional next spring which will support the creation of commercial games on the Xbox 360 using an Xbox 360 developer kit. Titles created with XNA Game Studio Professional by developers with approved titles will be able to be submitted for certification, unlike games made using XNA Game Studio Express.