I had to make two changes to get maxima to compile on abcl. First, insert abcl on this line of mforma.lisp
#-(or clisp gcl abcl openmcl) #\vt
Second, comment out the following line to avoid the error "The symbol MAXIMA::RUN is already accessible in package MAXIMA."
#-abcl (import 'cl-user::run)
Although not necessary to compile, you might replace the following so .abcl files do not go into an "unknownlisp" subdirectory.
(defvar *maxima-lispname* #+clisp "clisp"
#-(or clisp cmu scl sbcl gcl allegro openmcl abcl) "unknownlisp")
You might also insert in INSTALL.lisp insert a step between 8 and 9 "For developers, to run maxima without building an executable, enter "(run)".