To be fair, they don't claim they do free software. In fact they are explicitly against the FOSS movement as they say it supports the "oligopoly".

They use the term "open source" because the sources are available, but because of their disagreement with the OSI, they prefer "source first".

Their license is a proprietary, source-available, "donation-ware" type licence.

It is not my thing, but it is their work, they get to set the rules.