I compiled "Chris Nystrom's 'C' port of Mayfield-style StarTrek, 1995" and the only adjustment needed was renaming the getline() function (getline()->xgetline()) to avoid a conflict with stdlib.
I'd say it's expected, from what I see the version is in "ANSI" C. I can compile it as-is (without renaming anything) with gcc and it runs, it just warns that "register i" etc. are treated as integers, which is what they were intended to be anyway.