The community edition is free for individual developers, developers creating open source projects under an approved OSI license, or for up to 5 developers in an entire organization. Basically, it's not for production use by companies with more than 5 developers developing proprietary software. At least from my quick reading of the license: https://www.visualstudio.com/support/legal/mt171547
UPDATE: Community also excludes any organization with 250+ PCs or $1,000,000 or more in yearly revenue. (credit: icegreentea)