The latest release binary and source releases are always available on the Apache Commons Pool Downloads page.
Versions 1.3-1.5 depend at runtime only on a Java 1.3 or better JVM.
Commons-pool 1.2 depends at runtime on commons-collections.
Older releases are retained by the Apache Software Foundation but are moved into a special archive area.
Access to the source tree to see the latest and greatest code is possible through anonymous SVN access.