No, that would undermine the whole platform. The DTH code installed can only be viewed by you (and the ST staff) and control of devices is limited to your account (and those you invite to share your account).
It may be worth reading through the FAQ’s and Wiki’s on how custom Device Handlers and SmartApps work in the SmartThings environment.
The purpose of local processing is to reduce the timelag/latency and also help device control during internet outages. There’s a push from end users for ST to extend this functionality to custom apps and handlers as well (which I believe they are looking into but they haven’t given an ETA yet). The underlying security model is the same whether it’s a cloud DTH or a local DTH, it’s just a matter of where it executes (and the same goes for apps)