Looks like I've got the same task.

Been given a legacy DB that has been sitting on a shelf for 2 decades, and I'd like to extract data from it. It was a scientific research project.

I've figured out I've got *.4db, *.4dd files. I suspect the DB was developed and maintained in 4D 6.7.1 version on MacOS. I've tried installing the available 4D versions from the official website. Both v20, v18 give an error of "DB version to old".

Now, where can I obtain a trial/freemium copy of 4D app of 6.7.5, or at least some other version from the 2000's? The legacy versions of the software are only open for download to "dev partners" (that's a $300 license). Perhaps someone with access could help me get a freemium version of that era (pref. Windows version) so that I could attempt to access the data?