http://bugs.winehq.org/show_bug.cgi?id=5926
--- Comment #5 from Michael Hoffman blackdragon1157@gmail.com 2007-12-27 21:10:55 --- I'm assuming that an entirely new winhlp32.exe has to be written. If not, disregard the rest.
I'm not 100% sure of the licensing on this (it's listed as freeware in the included text file). It is a .hlp decompiler with c source. Included is (what seems to be) a full explanation of the .hlp format (I couldn't find the format anywhere else). I have no idea where to find it on the internet (After I installed MS VC++6, a friend gave it to me to help him with documentation for one of his programs). Wikipedia says that .hlp is a proprietary format, so I'm not sure of the standing on explanations of the format. If it interests anyone, I'll attach it (but I won't now because of the first argument up there).