I follow the link and download SDE 3.1 for VS community edition (installation file:VP_Suite_Windows_2_1_20060116.exe). But, when i try to install it, there is no option for VS. And, check the email for key, said it is a 30 days key, not free for community edition.
The problem is caused because the installer is unable to recognize your VS .NET. Could you please make sure you have installed Visual Studio .NET 2003 on the account which is going to install SDE-VS?
I regret that SDE-VS does not support VS 6.0. But we are now working on the support of VS.NET 2005 and it is now in the testing phrase, and will be available very soon. Do you want to have a try? I can arrange an early access release for you.