Reading Usable Help
@UsableHelp on Twitter
Gordon R. Meyer
Delivering Help in the "native" format for the operating system is almost always the right choice. It makes it easier to provide a consistent user experience, and built-in help systems are always better integrated with the system as a whole. But if you need to deploy a Help system on many platforms and simply can't afford to do the right thing, a cross-platform Help engine might do the trick.
An alternate approach is to use a utility that converts between Help formats such as QuickerHelp by Software MacKiev. Or use something like HelpExplorer by KAMA Software, which provides viewing of older Microsoft Help documents on Linux. (Thanks, Jenny.)