New features which should be implemented in Porteus; suggestions are welcome. All questions or problems with testing releases (alpha, beta, or rc) should go in their relevant thread here, rather than the Bug Reports section.
It is a wrapper for yacc and lex (from what I can tell). Using my google-foo, I found that ylwrap exists (in some form at least) in automake, gettext, and kdesk...if installing bison or yacc doesn't work, maybe try automake.
One of the best tools that I've found for developing is pkgs.org. They list a ton of packages, and they list every file and directory in a package. Their search tools aren't very useful for finding individual files (unless you use advanced search and know the full path), but google is. Use google's advanced search, search for ylwrap, in site/domain pkgs.org, and you'll see a list of linux packages with files containing ylwrap.
Please take a look at our online documentation, here. Suggestions are welcome!