We currently have two active codebases. ProEssentials v7 and v6.
Pick your version of interest:
1) ProEssentials v7 : Released on Feb 20th, 2010. We do plan on adding a few free features, and as always quickly resolving anything needing attention.
2) ProEssentials v6 : Released on Jan 10th, 2007. No longer getting new features, we will fix anything major in that rare case.
3) ProEssentials v5 : Released March 30th, 2003. We recently updated to resolve Win7 breaking v5 but no more changes are expected.