If you're looking for the ActiveEndpoints BPEL engine and associated tooling that we qualified against for ESB 4.2 and SOA Platform 4.2, then here is the information (the original URLs broke when ActiveEndpoints restructured their web site):

http://www.activevos.com/community-open-source-terms-conditions.php link
you'll find the following downloads of the open sourced server - they've kept
all prior releases of the open source servers (binary and source) available:

* ActiveBPEL 5.0
o Final Release -
http://www.activevos.com/community-open-source-engine-download.php#final50
o Milestone Releases
* ActiveBPEL 4.1
o Final Release -
http://www.activevos.com/community-open-source-engine-download.php#final41
* ActiveBPEL 4.0
o Final Release -
http://www.activevos.com/community-open-source-engine-download.php#final40
* ActiveBPEL 3.1
o Final Release -
http://www.activevos.com/community-open-source-engine-download.php#final31
* ActiveBPEL 3.0
o Final Release -
http://www.activevos.com/community-open-source-engine-download.php#final30
o Patches
o Milestone Releases
o Weekly Releases
* ActiveBPEL 2.1
o Final Release
o Patches
* ActiveBPEL 1.2
o Final Release