There's some confusion here (not your fault, is really confusing).
Some history:
There was a VTV port by Joerg Thaler,Christian Ulrich hosted at Lazarus-ccr. It used the approach to comment code that were buggy or not implemented in LCL. This lead to a largely incomplete port.
So i started a new VTV port long years ago at BountySource. I took another path: as soon as i hit a code that was buggy or not implemented in LCL and its widgetsets i reported in Lazarus bug tracker providing patches when doable. In parallel i created a support package implementing API that does not make sense in LCL (LCLExtensions). Sometime later i was asked by a Lazarus dev (Vincent) to move to Lazarus-ccr initially under the virtualtreeview-unstable repository, later renamed to virtualtreeview-new. The original port is still there.
Changes in VTV delphi repository were backported to the Lazarus port and were in more or less in sync by the times of 4.8 release. At this time Mike Liesche stopped working in VTV and development stalled. When work was resumed in 5.x branch, initially i did not backport. Only later i separated 4.8 from trunk in virtualtreeview-new repository and started to sync Delphi VTV 5.x/trunk with virtualtreeview-new/trunk. Since than virtualtreeview-new/trunk has became unstable because of changes in interface or windows specific code introduced while doing the backport.
Currently the virtualtreeview-new/trunk has most of the 5.x code ported but needs some work to get in a decent shape specially for non windows. With the move of VTV to github things will be easier since git has features that allows to maintain forks tracking and merging changes from the original in a structured way. Until now i was doing almost manually (with help of tools like araxis merge, smartsynchronize and meld)