They explicitly say it's not intended for reuse, and various stuff has been redacted (though I've not identified any that would stop the code from working). Interestingly you are allowed to reuse the code under the EUPL license.

It would seem so: https://github.com/MinBZK/woo-besluit-broncode-digid-app/blo...

The interesting aspect of this is that it can be studied to write clients for platforms that are not officially supported -- currently, only Android and iOS are supported, but it'd be great to see a Linux client too.

It's a big shame that history has been rewritten and heavily redacted though. Version control history often has a lot of contextual information that's not immediately obvious in the source code itself.

I dont think self complied version would work with service like belasting etc.

I did not look in depth, but the source code would reveal how thing are getting encrypted and business flows but not the data. That is in the digid's infrastructure

It appears any important strings have been replaced with 'S' characters.

So you definitely can't use this unless you pull the strings from the compiled APK theyve published.