If you are using an Okapi Tool after the M9 release, you should be using the wiki online help:
http://www.opentag.com/okapi/wiki/index.php?title=Rainbow
Include non-translatable text units -- Set this option to include the text unit that are flagged as non-translatable in the generated XLIFF document. Depending on the input document and the filter you are using, such text unit may have text useful for context. In some other cases, they may be just codes.
Set approved entries as non-translatable -- Set this option to
have the XLIFF translate attribute set to "no" for the
text units that have approved translation (that is that have an approved
target property set to "yes"). This may be useful when you are
working with an XLIFF editor that does not recognize the XLIFF approved
attribute.
Note that this option is available only when you include the non-translatable entries in the XLIFF output (because otherwise merging back the data could not work).
Use the <g></g> and <x/> notation -- Set this option to use the
XLIFF notation with empty content markup elements (<g></g>,
<x/>, etc.). If this option is not set, the notation with code content is
used (<bpt>, <ept>, <ph>, etc.)
Copy source text in target if no target is available -- Set this
option to copy the text of the source into the target XLIFF entry if no existing
target is available. If this option is not enabled, the <target>
element will be empty when no target is available.