You did read:
Frank has left us in 2011, there will be no original source code. The one published is as far as we can get. It is from someone with contact to Frank in the golden age. I didn't wrote 'original' source code. And objection: this is not a pure disassembly! There are many comments in the code, of course in German, but they are inside! A pure disassembly can't do that. All major points have comments, so the user can get into the code. Look at vitoco's work above and please wait for an assembly done with the Bibo Assembler. Stepe by step, one after another. Compare the Star Raiders code with the one from Lorenz. Sure, original ones have more value, but I inted to put the focus on more usability. Therefore, Altirra is a really good option, Basic++ is another, and Hypra-Soft-Basic. As posted before, interbreeding will give us the best verson available.
ijor, please don't mind, but I really don't want to go further here, there is too much on my list. When the digitizing project is finished and all source codes are in the can, we can continue here. But I will take your point, of course.