TL;DR* Here's what the license entails:
1. Anyone can copy, modify and distribute this software.
2. You have to include the license and copyright notice with each and every distribution.
3. You can use this software privately.
4. You can use this software for commercial purposes.
5. If you dare build your business solely from this code, you risk open-sourcing the whole code base.
6. If you modify it, you have to indicate changes made to the code.
7. Any modifications of this code base MUST be distributed with the same license, GPLv3.
8. This software is provided without warranty.
9. The software author or license can not be held liable for any damages inflicted by the software.More information on about the LICENSE can be found here
Yet another question: (Trying to protect my own software from being open source).
Suppose I set up a secondary processor, like an Arduino, and have some of MY software running on it. I have the open source code running on the primary processor and modifications I made to that open source code SENDS INSTRUCTIONS, perhaps by way of serial communications, to the secondary processor to have that secondary processor run its own software (that I wrote).
Is the software that I'm running on the secondary processor considered to be "part" of the open source code and therefore must also be made open source? Or can I (potentially) patent or copyright or otherwise protect that software I wrote that's running on the secondary processor?