Open source is enabling proprietary software to be more profitable, because it makes free all the commodity pieces that are needed to make proprietary software work.
Customers would otherwise have to pay for these things (in an ongoing manner) leaving less of their $$$ to spend on your payload.
Open source powers SaaS which is so closed and proprietary that the user doesn't even get to execute the binary code on their own hardware.
Of course, if your business is selling operating systems, development tools, databases and other infrastructure stuff, then, yup, open source has eaten your business.