CCDciel is free software released under the terms of the
GNU General Public License
You can install INDI with the packages provided by your Linux distribution, but as this is a rapidly moving project it is best to get the latest version directly from the project.
For example for Debian/Ubuntu see https://launchpad.net/~mutlaqja/+archive/ubuntu/ppa
For macOS the best option is to get the version from CloudMakers.