I'm about to buy the Pro version, and just wanted a simple straight answer to a few questions.

1) If I setup a Network Calendar, via FTP on my website, that I want to access from multiple systems (Home, work, laptop, etc), is that possible with a single license? or do I need to buya license for each copy?
2) Once I get the pro version, how can I "move" everything that I have hosted locally right now (on a USB key) into that Network Calendar?
3) The network calendar will support both Calendar & Tasks?
(I was going to use Google, but I see that rainlender won't sync tasks with Google).

1) One license is enough.
2) The network files are the same as in your local system so you can just copy the ics file to the server. Alternatively you can also import the events to the online calendar.
3) Yes.

Great!

Now, I see that the "Network" calendar interface says it supports ftp protocols, but i'm getting "Error 550 (file unavail)" every time I try.. Does it use the username/password to login to download the calendar? Or only to upload?

oh... I see if I set it to just "ftp://server/Default.ics" (Leaving out the Directory), it works. Odd. Is that a bug?

The way you access the file depends on how your ftp server has been configured.