The PLC/DCS/SCADA world hasn't really caught up to modern open-source software in a lot of cultural ways. Lots of proprietary components and "pay-to-learn" practices. I expect there's software-engineer types who would venture into the hard-real-time control systems world if it were as open-source and tinker-friendly as something like Rails. Nowadays someone like Microsoft has to go open source to have any hope of capturing developer mind share for something like .NET.