Quail 2.0 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The actual developer of this software for Mac is Cyaneous, Inc. Quail for Mac relates to Education Tools. We recommend checking the downloaded files with any free antivirus.
From the developer:
Quail is a convenient unit conversion widget for the Today view in Notification Center. Designed to be quick and non-intrusive in all aspects, Quail remembers the last selected measurement units for each conversion type as well as the previously entered conversion values.
You may want to check out more software for Mac, such as USA-Manual-Mac, Bible Sander or Biology, which might be related to Quail.