It is legal to create a utility that encodes a file based on another. It is NOT legal to create a program that creates a file with Maz's PCF format without Maz's permission. Both written code and algorithms can be legally protected; the algorithm would be necessary to create a PCF file, even if the code is altered. So, it depends on whether MartinC is making a program that produces PCF files or a file format that is a derivative/expansion of the PCF format, or one that is based on the same idea but is completely different and wholey original. His original message is rather ambiguous towards that.