In the latest Live Letter, Yoshi-P had this to say about Free Companies:
I see some things here that like, (leveling your Free Company, shared storage, alliances, etc.) but I also see something that I'd really like clarification on from the devs.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.
Are Free Companies tied to the Grand Companies? Meaning, is it going to be required that all members of a Free Company belong to the same GC? Are we going to be able to have members be from all GCs? I'd really like to get some clarification on that, since if, for instance, all FC members have to be Maelstrom, or if our FC's allegiance is tied to just the Maelstrom that's going to make a lot of people in my LS upset. I also don't want to have to run 3 different FCs to accommodate all of my members.
I know that FCs won't be in the game at launch, and are coming soon after, but the more information we can get about them, the better. As a LS leader, I'm going to need to be able to plan in advance for my members, and I know I'm not the only one out there with concerns about how the new "guild" system in ARR is going to work.