The format itself is patent-unencumbered. That doesn't mean I couldn't still write a non-free decoder and license it to Pioneer for use in their CDJs. Due to organizational inertia, I suspect that's what's going on here (e.g., they licensed a decoder from Fraunhofer or another commercial implementer twenty years ago, and have been using the same one since).

In this case, everyone at Pioneer knows their CDJs are used almost exclusively for commercial purposes, and perhaps they couldn't get away with lying about it in the fine print.