Incanto Ant Tasks for ESRI ArcSDE is based on the ArcSDE Java API. Therefore, to use these tasks, the JAR files included within the ArcSDE DevKit needed:
To install the task library, just put the Incanto JAR file and the ArcSDE JAR files (from the ArcSDE DevKit) into Ant's lib directory or classpath.
In your build file declare a namespace (eg "sde") for the Incato task library.
<project ... xmlns:sde="antlib:net.sf.incanto.arcsde">
The Incanto tasks can be used together with that namespace prefix.
<sde:registertable ... >