Nothing exciting. als commented that he likes some FUTO software, among other things because it’s Open Source, and I responded that it is not.

I meant the definition by the Open Source Initiative, but in almost all cases, it doesn’t make a difference if you use that or the FSF definition.

The license shall not restrict any party from selling […] the software

it may not restrict the program from being used in a business

In addition to the restrictions on commercial use, the FUTO license says that you may not remove payment logic and then share your modified version, which might also be unacceptable for the FSF and/or OSI.

It is not Open Source, it is “Source Available”. The Open Source definition requires that users get certain rights that the FUTO license does not grant.