The latest JAR can be obtained from the Codehaus Maven repository. The repository also contains project assemblies, which include the source code, generated JavaDoc, and dependency JARs.
Download the latest snapshot here.
Download the latest stable build here.
Maven users can simply copy the dependency tag into their own project:
<dependency> <groupId>org.codehaus.groovy</groupId> <artifactId>http-builder</artifactId> <version>0.2-SNAPSHOT</version> </dependency>