WordPress Usage Permissions

Hello,

We have seen on many sites that they used “WordPress” software on their news channels sites and blog sites. some sites are commercial and some not.

we are also interested you used WordPress software for our company sites because its simple and quick.

But i need some questions clarifying first.

Word-press is a free software or it required some license ? according to read this is GPL. but no copyright removed. but there are too many legal organization which run WordPress software without its copyright. so can they purchased it ? or its have license to do that ?

can we used it commercially and for business purpose ?

Is there any thing which you want to recommend me before start site on this software ?

Thanks