Irrlicht Engine

AFAIK, interpreting anything is not illegal, so decompression is no problem here. However, compression can be a problem, as you have to take a rather unusual way to handle your so far plain data. This also holds for all those other file format patents, and even for Microsoft's FAT file system patents

If that were true Mesa guys would have added this years ago. Unfortunately it's just the other way round - compressing is legal - decompressing isn't/wasn't in this case. And the patent owners have in this case rather aggresively defended that, although yeah - recent lawsuits have put the patent in doubt. So I think current solution with having a define around it so users know what they get into when they enable it is fine.

In rev4450 we finally added DXT texture compression support in Irrlicht. Also DDS loader is clean, _IRR_COMPILE_WITH_DDS_LOADER_ is patent free and it's enabled by default. _IRR_COMPILE_WITH_DDS_DECODER_LOADER_ is disabled, because it's related to patent problems.

BTW. After define _IRR_COMPILE_WITH_DDS_DECODER_LOADER_ compressed textures will be decompressed by Irrlicht, so You will lose all benefits of compressed textures.