This project is licensed to you under the terms of the GNU General Public License v3
What this means in practice is that if you extend this code in any way, you are obliged to share the source code with the community. You can't just make a derivative product and distribute it through Google Play in binary format only.
You can browse the source code using the Github - Lumicall repository
Please see the file BUILD.txt for step-by-step instructions
If you are developing with Lumicall and want to participate in the community, please join the mailing list for developers.