Yes. In the horizontal industry organization, products ran across brands, or across different stacks. So, MS DOS and Windows ran on IBM, DEC, Compaq and many ot

Yes. In the horizontal industry organization, products ran across brands, or across different stacks. So, MS DOS and Windows ran on IBM, DEC, Compaq and many other PCs. Competition was between Microsoft and IBM etc (OS), Intel vs AMD, WD vs Seagate, OSI vs SNA vs TCP/IP etc. These battles usually ended up with one big winner, as you would expect from power laws. Things don't have to be open source to be de facto standards, just openly licensed, eg Windows. The use of proprietary connectors is a common feature of vertically integrated stacks. As I used to say, Apple is just DEC by other means. Modern ecosystems are different from the old vertical stacks because (among other things) they're cross platform. For example, Microsoft has dozens of apps on Android and iOS.