after I fixed some broken connections on my self-etched PCB, it seems to work so far I could test. I tested an ATTiny 13, an ATTiny2313 and an ATMega8, so it should work with their respective MCU-families, too. I could not the ATMega 16 and ATTiny 26 family (but I think they should work), so if anybody rebuilds this project and test these MCUs i would be pleased when you write a comment.
I have released my design files under the CERN OHL v1.2 License, you can find them together with my modified bootloader and firmware code in this (https://github.com/jbtronics/AVR-ZIF-Programmer) GitHub repo
Finally some images of my board. It is self-etched with Sodiumpersulfate using the toner-transfer method. With the same method i put some silkscreen like print on the board. Additionally the board was tin-plated using some fittings solder paste: