See this about Jam on Mac.
“unzip main.zip” produces directories “__MACOSX” and “main”. I don’t know what that’s all about. There is little of interest in __MACOSX. The content of main is plausible.
I “cd main” and “jam”. The first problem is that this version of gcc does not know the “-mv8” option which directs the compiler to produce SPARC code for model v8 SPARCs. This is no surprise. I delete line “CCFLAGS = -mv8 ;” and subsequent text “-mv8” from Jamrules.
Source file src/kernel/sun4m/genassym.c wants header keyh.h . src/include/sparc/keyh.h is the right file, I think. I don't see the command line for gcc. I guess I must learn some Jam.
I remember thinking that the tree of .c files was poorly organized. This was a result of shifting concepts of modularity over several years. I might try a flat directory for each of