This question seems to say that it's necessary to root an at&t phone (like the samsung captivate) in order to install apps from unofficial sources. My question is a bit more focused: if I'm working on my own android app, will I be able to load it on my at&t phone for testing (via the android SDK, etc.) without first rooting the phone?

I'd like to try out some Android beta software I found online, but when I tried installing it on the device I got a message that said that installing non-market apps has been disabled for security reasons. Can I bypass/disable this restriction? I am using the at&t Captivate (Samsung Galaxy S) with Android 2.1.