As of a few minutes ago, we’ve updated the front page so that the “Get Vassal” button now tries to present you with a direct link to the correct download for your system.
For example, I see this when using Linux:
If you’re using Windows or macOS, it will try to identify which architecture your CPU is in order to give you a download to match. Should this give you the wrong download or fail to identify your system when there is a correct download for you, I’d like to hear about it here.