Commons Pool currently has 3 active versions:

+ trunk, e.g. 2.x (not released as of mid June 2012)
Targets Java 1.6+

  <groupId>org.apache.commons</groupId>
  <artifactId>commons-pool2</artifactId>

Not compatible with previous versions.
Uses new Maven coords (above) and package name
org.apache.commons.pool2

+ branches/POOL_1_X, e.g. 1.6
Targets Java 1.5+

  <groupId>commons-pool</groupId>
  <artifactId>commons-pool</artifactId>

+ branches/1_5_RELEASE, e.g. 1.5.x
Targets Java 1.3+

  <groupId>commons-pool</groupId>
  <artifactId>commons-pool</artifactId>

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Note.
To edit this file, check out "files-only" or "immediates" from
https://svn.apache.org/repos/asf/commons/proper/pool