SpoilerZAM Question #11: What are Free Companies, and how will these be structured? Are these the player-run companies we heard about in the past?

Yoshida: "These are player-controlled companies. You can think of it like the guild systems that a lot of other MMORPGs have, the player-run guilds. Think of it as each player, for example, five people can be a Free Company. I can be a member of the Order of the Twin Adder, he can be a member of the Maelstrom, he can be a member of the Immortal Flames, but we can all get together and make our own Free Company. Individuals can do the Grand Company content on their own, and then we can make this Free Company with a lot of people from different companies. And also, the Free Company can sign up to join the Grand Company, so you can experience Grand Company content through your Free Company, even though if I'm in Gridania but our Free Company signs up to work with the Maelstrom in Limsa Lominsa, then we can do those contents as well. That's one thing where players will be able to cross over.

"So when players make their own Free Companies, they can decide what they want to do. They can go, "OK, I only want to have people from the Order of the Twin Adder be in my Free Company, and their Free Company is going to be hardcore, or they can have a mixture of lots of different players. That will be up to the players."

ZAM Question #12: Can people experience all the company content through Free Company participation, just by signing up with all the different companies?

Yoshida: "The content will be different. There will be the Free Company content of the Grand Companies, as well as the solo content of the Grand Companies. You'll only be able to do the solo content of the Grand Company you're in, but when it comes to the Grand Company content that's for Free Companies, it won't matter as a solo player which company you're in, it will matter which Free Company you're signed up with. It will be two different stories."

http://ffxiv.zam.com/story.html?story=28045

Spoiler
F: Please explain the details of free company
Y: First gather with 4 people - get in grand company - go to grand company counter and apply for free company and that’s when it will be created. At that time you will have a shared box which is shared with the 4 and have for example company leader which can only take out items from the box and stuff. It has detailed option so you can set those. By completing contents your free company level increases and you can create more emblems or have other features to expand. You can make a free company with 8 static members but say you can have allie with another company where you can share BBS (forum) and stuff together it has lots of options.
Y: You can also join company as a guest to try out the company and see if you like the company or not. Also you can invite low level players and by helping them you get points and stuff. It’s not too strict but one thing is you can’t have multiple free company as we have issues with shared items and stuff so that will be there.

http://forum.square-enix.com/ffxiv/threads/54391-Free-Company-Information