The need to define symbol CASTLE_ENGINE_LGPL to get LGPL engine (otherwise you only had GPL) disappears. The whole engine can be used on a permissive LGPL terms out-of-the-box now, there is no point in defining the CASTLE_ENGINE_LGPL symbol anymore.

I have clarified and simplified our license terms on https://github.com/castle-engine/castle-engine/blob/master/COPYING.md . In short: we’re exactly like FPC and Lazarus. Yes, you can make closed-source applications using CGE.

We have a new NURBS implementation, developed by Michalis from scratch. I deleted the old (GPL-only, copyright by White Dune developers) implementation in this commit, and later implemented new one (LGPL, copyright by me) in subsequent commits. So the LGPL engine supports NURBS now.

The new implementation also got some serious optimizations (utilizing the fact that we usually calculate not one point on a curve/surface, but a number of such points in a series).

The new implementation also features a helper method TNurbsCurveNode.Point. See this test for a quick usage example. This allows you to use NURBS curves calculation for any purposes, not necessarily by placing the NURBS nodes inside TCastleScene.