You can but in reality it's not something you would want to do .. in the early days we tried it with a small webapp, but the code you get out of it is not easy to maintain or change, you can however keep the website running without the outsystems tools, and in the mean time create a new solution .. but in the end why you would want to do that.. going back to .net or whatever solution Microsoft is offering currently isn't comparable with the offer of OutSystems, also good ..net developers will be harder and harder to find and will come at a big cost.
regards,
Wim