The Software Patent Threat
Software patents threaten practically software development projects, be them propriatory or open source, the OpenSceneGraph is no execption. Software Patents are legal in USA, Australia and Japan, but also have a rather dubious legality in Europe. Currently the European Union are processing legislation that could either ratify the move to legalising Software Patents that patent professionals and some multi-nationals have been driving for, or instead to reaffirm the non patentability of software that was original part of the Eurepean Patent Convention.
The way the Software Patents directly affect the OpenSceneGraph project is that both the core developers, developers that use the OpenSceneGraph for their application development and their end users all are open to the possibility of litigation from agressive patent entities. These patents entities may take the form of a company trying to destroy or damage a competitor by preventing them from using, distributing and selling their software, through to entities seeking rents - the price of which is determined by the greed of the patent entity, not free market forces.
The less obvious effects on the OpenSceneGraph project are the features that won't be developed simply because of known patents covering areas of interest, there is already several areas where development work has been curtailed, and as the patent thicket grows thicker this is only likely to become worse and just avoiding the patents will take more and more of our time slowing development.
So far the OpenSceneGraph project has escaped any major detrimental effects of software patent, but this is not something we can assume long term. Other open source projects have already been forced to be stopped entirely or have features dropped because of recieving cease and desist letter from patent entities, a recent example was the VideoLan project dropping support for a particular codec, but also include FreeType dropping support for high quality fonts, GNU compile not implenment certain optimization - all of which directly affect many OpenSceneGraph users. With the OpenSceneGraph become ever more popular the visibility as a target for litigation increases.