Having multiple implementations wasn&#x27;t a problem for Java (Sun JDK, IcedTea, JRockit), noone thinks much of the different compilers available for the C family (GCC, CLANG, Microsoft C compiler, Intel&#x27;s C compiler), consider Ruby with MRI, JRuby, or Python. I could go on.<p>Members of the Lisp family seem to be judged by a different standard. I don&#x27;t know why that is.<p>My perspective: the implementations attest to good documentation and collaboration. SBCL by itself is an admirable artifact with extensive documentation that&#x27;s been maintaned since 1999 (when it forked from CMUCL).<p>So what gives?