I came across a post (from TheServerSide.net) regarding an issue between TestDriven.Net and Microsoft.
I think this typifies the general difference between 'open source' development platforms and 'closed source'. Microsoft's main concern here appears to be driving people to purchase full versions of Visual Studio by handicapping Visual Studio Express (which is free) as much as possible. You could argue it was 'nice' of them to release it at all as a free option, but who am I to give Microsoft credit. :)
Even if Microsoft is legally correct here (which I think the intent is, but the language is VAGUE), it just seems like a stupid move. Microsoft is successful because they own the platform. The Operating System, Office, Exchange, Etc. It all ties together and is of course optimized to work with all the Microsoft tools.
If you look at Microsoft's revenue breakdown for 2006, you will see that 'Servers and Tools' make up 22%. I believe (but have no specific facts) that the tools portion of this is a minor part.
Microsoft would be better served to just release all the developer tools for FREE and drive people to use their platform. By upsetting and criminalizing their developers because they develop useful tool for the 'free' version is just wrongheaded. Even if they don't release them for free, it doesn't seem to make sense to actively pursue this fringe revenue.
After all, I thought it was all about the developers.