When I read articles like this my question is always, if it's open source, why doesn't a competitor simply grab a slice of the source code, integrate it into th

When I read articles like this my question is always, if it's open source, why doesn't a competitor simply grab a slice of the source code, integrate it into their own closed source commercial product, without complying with the license? In a scenario like this if you are a small company with little resources it's impossible to find all those who violate the license and pay for all the lawyers to enforce the license.