Can I use the GNU General Public License in my Business for free?

[SkEgY]

Is this legal?

[Pichurri]

You can use the software licensed under GNU license, not the license itself. The GNU licensed products (the source code) are free and you are allowed to modify it, but only if the resulting product is licensed under GNU too.

[John K]

Yes. The main requirements to the GPL are that if you make changes to improve the code then you need to submit those changes to the GPL holder and that you give credit for the software to the GPL holder.