GPL
1. You may copy and distribute verbatim copies of the Program\'s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copy right notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any war ranty; and give any other recipients of the Program a copy of this License along with the Program.
You may charge a fee for the physical act of transferring a copy,
and you may at your option offer warranty protection in exchange for a fee.
2. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section1 above, provided that you also meet all of these conditions:
a. You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.
b. You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.
Basically, you can charge or whatever you want but you must make the source code available. You can also take GPL code and make a comercial product, but any changes you make to the code have to be available upon request.
