desertman asked:
"I'm wondering whether it is possible to install OS X 10.6 in a virtual machine on a Mac with OS X 10.11. Anybody having any experience with that?"
I haven't done it, but the following works:
1. Install a virtual machine app, such as Fusion or Parallels.
2. Install a copy of Snow Leopard Server (you MUST use the server version, regular 10.6 won't run via emulation).
3. Turn off server features and just run it as a "regular copy" of the OS.
This method will run 10.6 fine, I hear.
Aside:
Unless you really, really need to manipulate data within these old database files, easiest thing to do is use LibreOffice as mentioned above.
Then either view the data in spreadsheet form, or import it into a "modern" database app...