What does availability mean?
If three peers have 50% of all pieces but they have the same pieces, is the availability 0.5 or 1.5?
https://wiki.vuze.com/w/Availability suggests that it would be 0.5.
The major number of the Availability tells you how many copies of the least available piece of the torrent you currently see.
But then how is the fractional part calculated?
That Availability > 1.0 condition can be also reached with several peers having different pieces of data, so that combined they have all the pieces.
If there are no seeds, how can availability exceed 1?