The S3TC Patent Finally Expires Next Week - S3 Texture Compression
S3TC has been a thorn in the side of open-source graphics driver developers for years. It's resulted in a nasty wreck that's long been problematic for both drivers and users from a legal perspective.
S3TC is a lossy texture compression widely used by many games and this compression method from S3 Graphics has been in use for many years going back to the OpenGL 1.3 and DirectX 6.0 days. In the OpenGL space it's provided by EXT_texture_compression_s3tc and without the support the performance/quality can be worse. S3TC support hasn't been present in Mesa by default due to the patent situation while there has been the external libtxc_dxtn library.
Come 2 October, the S3TC patent is expected to expire with the earliest filing date on it being 2 October 1997 and the expiry period being after 20 years.
Thankfully these days there are patent-free, royalty-free texture compression alternatives like ETC2 and ASTC, but S3TC is still used by a fair amount of software out there.