CLion is a commercial product built on our own open-source IntelliJ Platform. As all other JetBrains products, CLion has a variety of licensing options, including free and paid ones. Students and open source projects qualify for free licenses. CLion is also available as a part of All Products pack. Startups can get 50% off. Check the details on our site. However, community edition is not planned for now.
In the future, a CLion-based plugin will likely be made available for IntelliJ IDEA, but this is not on our short-term roadmap due to many requests with higher priority.