There are many popular patented compression algorithms or transforms like LZW, Arithmetic Coding, Schindler's Sort Transform (STx), MP3, probably LZX and many others. They were patented a long time ago and patents last limited time. Is that true? If so, then most of them should be now invalid and algorithms should be free.

I am implementing STx and BWT transforms in OpenCL and I'm curious if I have to pay for licence if I want to make money on it.

And what about Range Encoding? It's basically equal to Arithmetic Coding from efficiency perspective, but different in many details.