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
If you create a derivative of a GPL work, that derivative must also be GPL.
You can add additional compatible licenses, but all of them have to be obeyed at the same time. Only an original work may be dual licensed, and allow the person making the derivative to pick which one.
Licenses are compatible if requirements don't conflict with restrictions.
If one license says "you can't" and the other one says "you must" for the same action, then the two are not compatible. "You may" and "you must" are compatible (this means you must), and "you may" and "you can't" are compatible (which means you can't).
The only way you can remove the GPL is go straight to the copyright holder of the original work, and request source under a different license.