Sorry, Androids do not support .jar files. I'd suggest search for the apk file of the app you want to install and then download it and astro file manager from android market use android market and use WiFi to download the app on your phone
I heard that T-Mobile rolled out Android 2.2(froyo) updates OTA(Over-The-Air) over Europe and US but they did not specify about Netherlands. But to update on my DEFY I had to go About Phone-->Options-->Search for updates. t gave me an 122MB update. I put on WiFi and downloaded it. It's a major...