Like WordPress, bbPress uses a semi-decimal-based versioning system, where bbPress 2.4, 2.5, and 2.6 are considered major versions.
bbPress 2.6 was a major update with just under 6 years of development:
This version of bbPress has been in development for just a bit under 6 years (yikes!) over which 420 tickets were resolved via 1737 individual code commits.
The Full list of releases is available on the bbPress codex, although it doesn’t have the full details for the latest two minor 2.6.x releases.
