> But after a few minutes it occurred to me that I just did free labor for a for-profit trading company. If they merged in my code then must have thought it had some value, and I decided to dedicate my time to saving this multi million dollar company some money.
If you're not ok with that possibility than you probably shouldn't be participating in open source.
And to be clear, there is nothing wrong with that. Its up to each individual to decide how they want to spend there time. There are pros and cons to open source, and you have to weigh how you feel about them yourself.
However, its not like this is some secret trick. Its the central tenant of Open Source (esp. When using that name instead of Free software). It should be very clear that this is happening. Its the entire point.
It kind of feels a bit like someone who doesn't like oranges, eats oranges, and then are surprised that they taste like oranges. By all means if you don't like oranges don't eat them, but if you knew you didn't like them why did you eat it in the first place?