So anyone that refuses to pay for their tools will eventually either loose them, or contend to be happy to use lesser ones.
It is certainly not confusing it you learn it by rote and remember the rule. It is burned into my brain, but I see the mistake a lot so I assume it is hard to remember for some people. For me its vs. it's is something I still have to keep looking up.
Open source software is clearly a net positive overall. However is it a net negative for the industry when enterprise developers rely on open source software without demanding their company provides financial support for that software? How is that different than the company relying on free labor from something like unpaid internships?
Speaking for my own open source projects; There are already better, cheaper, and easier alternatives to my software. I'm already paying out the ass for something I could just download. I'm doing it for reasons that I can't, or won't, buy. And I know that sounds cliche because it is cliche, but passion is cliche.
We're programmers and hackers here. Just like a hot rod enthusiast spends $200k and 3 years building a car he could buy in a catalogue for $75k; we don't pay as much attention to cost/benefit relationships as we'd like to think.
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.
In my company an intern conducted research on scalability - creating tools to measure and monitor the software in the mean time. So not only does the company have some neat monitoring tools now, the intern actually found a bottleneck and improved the product. The company is now offering her a contract...
Caring about eachother doesn't have much to do with it.