LuxRender v0.x and v1.x
LuxRender was based on PBRT, the unbiased raytracer developed by Matt Pharr and Greg Humphreys for academic use. Pharr and Humphreys were kind enough to provide the source code of their program under the terms of the GPL, thus making the program free software.
In 2007, a small group of programmers led by Terrence Vergauwen took on the challenge to modify the program and make it suitable for artistic use. Late 2007, the initial version of LuxRender was released. With the release of LuxRender 0.5 in June 2008, the program was considered to be usable enough for general use. Since then, the rendering speed and the number of features and available exporters has been growing steadily.
LuxCoreRender v2.x
The plan for LuxRender v2.0 has been defined during the 2013 summer and one of the major components is a new LuxRender C++ and Python API. The old C API suffers of many limitations when it comes to modern features like dynamic scene editing and interactive rendering so it has been decided to write a completely new API instead of improving the old one. LuxCore is the name of the new C++/Python API. It offers all the features shown by SLG (aka SmallLuxGPU) in the past (in terms of dynamic camera, textures, materials, objects, etc. editing) and more.
During the 2017 winter, LuxCoreRender v2.0 was defined as a LuxCore API focused render package, dropping any old code related to LuxRender v1.x. A new web site, forum, wiki, Blender exporter, etc. were developed in order to mark a new fresh project re-start.
Lux(Core)Render is a 10+ year old opensource project.