Thank you very much!
Yes I read that license, although I was unsecure if I understood everything correctly.
Openpak128, do you mean the pak which exist in this directory: http://sourceforge.net/p/simutrans/code/HEAD/tree/pak128/
Regarding the credits, I will of course write the credit of original authors! Do I need to write that in a special place, or is the "copyright" sections in each single dat-file enough?
I was foreseeing a credit-strategy like this:
.png's and .dat's I havent touched at all will keep their credit/copyright section in their .dat-files without modification.
Original .png's but with modified .dat-file, Im unsure how to credit. Both me and the original author perhaps?
.png's I have edited will have both my name and the original author
.png's where i have modified every single pixel and Png's which I have painted all the way from scratch, I will put my name in the .dat-file.
Would that credit strategy be sufficient?