Build system: 

JDK required: 1.5+
Ant (http://ant.apache.org) required: 1.7+ 
(maven-ant-tasks-2.1.jar is required in $ANT_HOME/lib - download from http://maven.apache.org/ant-tasks/download.html)
OR 
Maven (http://maven.apache.org) required: 2.1+
 
IDE integration:

Ant is supported by all major IDEs.
Maven Eclipse (http://m2eclipse.sonatype.org/update):  builds classpath based on the dependencies declared in the POM.

Maven Build profiles:  

- default: builds all releasable modules
- reporting:  builds reports
- distribution:  builds distribution
- examples:  builds examples
- gui:  builds examples that require non-headless mode (separated as they do not run on CI: http://builds.codehaus.org/browse/JBEHAVE)
- nt: no-test, builds skipping unit-test behaviours 

Note:  profiles are additive and the default profile is always active.
E.g.: 

- build core and all examples 

mvn install -Pexamples,gui

- build with reporting and distribution:

mvn install -Preporting,distribution 

Building a release with Maven:

- mvn release:prepare -Preporting,distribution
- mvn release:perform -Preporting,distribution