I'm now ready to embark on ANTLR (and ANTLRWorks) code development after 2 years in book-writing mode. I've come to the conclusion that we need to completely rebuild ANTLR v3, yielding v4. After I finish, I'll update The definitive ANTLR reference book for v4.
The antlr tool itself is only 31k lines with 21k lines of unit test code (about 1000 tests). The Java runtime library is 14k lines (which we wouldn't have to rebuild). There are 2700 lines of templates for the Java code generator.