How is having a passion for a particular piece of software different than having a passion for a specific job or company? Plenty of people have enough passion for an internship that they are willing to take it for free. However society has been discouraging that over recent years because that route is only available to people who have outside financial support and it can easily be abused by employers. Open source software has the same potential drawbacks.

Not every piece of open source software is diminishing the value of enterprise software developers just like not every unpaid internship is reducing the value of entry level labor, however both systems can easily (and even unintentionally) be abused by businesses.