

This procedure is one hundred percent legal in most countries, but compiling programs is not common to almost any user (and not always trivial even for experienced developers). Since the developers of many codecs do not want to or cannot accept patents and possibly due license fees, they only provide the source code of FFmpeg, which you have to compile yourself to a finished program.

However, the use of FFmpeg also has its "price". That's why FFmpeg is now used in an astonishing number of (and even many commercial) applications. The special thing about FFmpeg - besides its open development with visible source code - is the wide range of supported codecs. Who shouldn't know it yet: FFmpeg provides numerous codecs and tools for processing audio and video, which can be used independently (standalone) or as functions of other programs and applications. Universal codec kit - FFmpeg 4.0 is here
