I believe we are having this discussion from a purely technical perspective and not from a business one. Let's take slack for example. Assuming a company can perfectly clone it, why would they? Yes they would skip paying for it, but they would have to maintain it, starting from its infrastructure all they way up to its UI. Will they think of new features? Will they follow industry developments in sound / streaming technology? Will they keep integrating other tools into it? I am sure they would rather pay to have somebody else do it for them, someone like slack itself.

Also, assuming a company has the capital to burn through enough tokens to create something so big and complex, why spend it on an internal tool? Shouldn't they be spinning slack-sized apps to expand their existing market share or try to disrupt new markets?