You could, and then you could wait. The "download" button is actually a "request invite" button:
Sign Up for an AeroFS Invite
AeroFS is still in early alpha/beta. Please enter your email address below and we'll invite you as soon as we can :-)
Sign Up for an AeroFS Invite
AeroFS is still in early alpha/beta. Please enter your email address below and we'll invite you as soon as we can :-)
That being said, we _are_ releasing invites on a fairly regular basis (usually coinciding with new bug fixed versions, in an effort to improve the overall user experience)
JungleDisk (like most other players in this space) requires you to upload your data to their server first, before you're able to sync it to other devices, where as using AeroFS, you're actually syncing data completely peer-to-peer (e.g. even on an isolated LAN), without a third party server, unless you want one
We didn't really expect the level of demand that we've had at our initial announcement ~144 days ago. Nevertheless, we've been pretty hard at work, and we are looking to ramp up invitations in the near future, but for now I can only implore you to bear with us :-)