If we are talking about RPOW and Bitcoin code, can you tell me where the significant differences are?
There are many different things.
1. Hal used multi line comments "/**/", while Satoshi used single line comments "//".
2. Hal added a new line after function return type, while Satoshi put it in the same line.
3. Hal used pointers "*" from C, while Satoshi used references "&" from C++.
4. Hal used Apple preprocessor macros, while Satoshi used Windows preprocessor defines.
5. Hal wrote it in C, while Satoshi used many features from C++ standard library, for example std::pair and std::map.
And so on, and so forth. The code is written in a completely different style, using completely different tools, and even different Operating Systems.
Even if you compare Satoshi's code in C, from the whitepaper, then it is formatted in a completely different way, than Hal's code in C.
With the differences you mentioned, is it impossible for someone like HalFinney who has experience with the concept to do it?
HalFinney developed RPOW in 2004, is 4-5 years not enough time for someone like HalFinney to implement it in another way?