Looks like a pretty clear violation of the WinDirStat license. They took WinDirStat which is GPL, linked it with some other proprieraty code and distributed the result.
(They could have been clear-ish (with caveats) by distributing only the source code and let the users do the compiling and linking, similarly to how you could download ZFS and build it into Linux. But you mustn't distribute the result further.)
(They could have been clear-ish (with caveats) by distributing only the source code and let the users do the compiling and linking, similarly to how you could download ZFS and build it into Linux. But you mustn't distribute the result further.)