Untill 2018 the class definitions in PRTools have been distributed as p-code. From 2019 all routines are supplied with the full source. The below is thereby just relevant for the older PRTools versions (before 5.4.2) that might still be around.
We distribute PRTools with p-coded versions of the routines in @dataset, @datafile and @mapping. The m-files in these directories just contain the help info. There is nothing secret about the software. Given the documentation you can even write or reconstruct these files easily yourself. If really needed why can also send you the m-file source.
The reason why we do this is that we want to avoid that different, incompatible versions of PRTools will be created. As a consequence we try to correct any bug, or any strictly needed upgrade as soon as possible.
The p-code compiler of Matlab changed some years ago. We distributed PRTools with the new p-code from release 4.2.1. The last version with the old p-code, needed for older Matlab releases is 4.2.0. It can be downloaded here.