I would say it is to Dash what ETH is to Bitcoin. The founder of ADA was also a cofounder of ETH. ADA is a public blockchain with smart contracts just like ETH. It's target market and functionality is thus slightly different than DASH and should be able to co-exist.

Unless you were able to patent such systems then anyone can replicate it and doing so is not really the issue. It's like back in the early 1900s when all cars used a tiller system. The tiller had obvious limitations so someone designed a steering wheel. Wheels had obviously been used on ships/ boats so It was not entirely a new concept. It was however such a fundamental that you could not really prevent other auto makers form adopting it. Certain aspects of the mechanical systems that make up the steering rack and then later advances such as power steering could be patented. This is like the computer hardware that is used to run the nodes. Chipsets, CPUs, GPUs can all be proprietary.

If you take the car industry as an analogy then in the early 1900s there were 100s of car manufacturers in the United States. Just because one had a steering wheel before the other did not mean that the company was safe form competition. It was the companies with the full package and greatest momentum that survived while others dropped out of the race.  

https://en.wikipedia.org/wiki/List_of_defunct_automobile_manufacturers_of_the_United_States