Open-source software has gone from being esoteric technology to the center of enterprise IT infrastructure, Eric Knorr writes. "Hadoop is at the center of the Big Data trend. OpenStack has the momentum in private cloud. Open source frameworks and IDEs absolutely dominate app dev, while all the leading NoSQL databases are open source," he writes. Open source has become so critical that it's being fought over by VMware, IBM and other big vendors, Knorr writes.