My blog stats tell me that there is a steady stream of visitors looking for Natara Bonsai, ever since the main download site has disappeared a few months ago. It seems that there is still at least one site where Bonsai 5 Desktop Edition can be downloaded from (and there may very well be some others out there). I don’t know whether this site is legitimate, so download anything at your own risk, and make sure you scan the file for viruses. However, I know of at least one reader who has done so, and he sounded happy. Here is the link: http://126.96.36.199/Bonsai/Download.cfm. It seems to be some sort of a mirror of the original site, as it looks identical. If you do not have a license, you could try to contact the administrator of the Natara blog to find out if it is still possible to purchase one.
Natara Bonsai is one of my old time favourites. While there are some other capable outliners out there, when I need to analyse textual data in long and complex lists, none are as easy and fast to use as Bonsai. The last version I have is v. 5.0.3 Build 3233. I run it on a Win 7, 64-bit machine, and it works perfectly.