Reality Factory

http://snappytree.com/
I found it through what may be the offline version at https://github.com/jarikomppa/proctree
and i think i heard of it these days from the devmaster mail news settler.

Exports to Wavefront .obj and collada .dae.Gives a message that you need o re appply UV after export.
If you are looking for a quick way to reduce the overall polycount ,every now and then go to the Tree tab and adjust the branch segments and level depth.

I know the leaves sheet polygon elements should not touch each other or any other mesh they are attached to,or you get transparency flickering and darkening in RF,but it is nice to play with.
If you have the patience,you can re position new branch polygons that do not intersect yourself.

About the transparency issue,am not sure if it has changed over the years but i remember i did a trick to optimize a whole area of trees and foliage and attached all before export as act and used invisible clip bsp brushes,
I think the transparency stopped messing when i added all transparent textured polys as a different actor,and that way the bushes could go deeper under the ground polygons.

http://arnaud.ile.nc/cantree/generator.php
I am checking the twigs modeler it used for the branch textures.It creates trees you save as .png image.
I do not know well enough to use it and i keep lose the centering of the branch,and it needs cropping again in a photo edit program.
However,there are branch textures made with it somewhere and am looking for any,maybe opengameart has some.
at least,the happy and snappy tree creates solid mesh trunk and trees mesh is one piece smooth,unlike many free tree generators that make each branch as another element.