This works fine with simple action=print for one individual page. However, for action=typesetpublish (trail page) the xml always contains the standard language regardless of the userlang parameter. In the latter case pmwiki.php MarkupToHtml or PrintFmt functions are called by wikipublisher.php HandlePublish, PrintRetrievedText etc. without $GLOBALS['userlang'] to be set correctly.
Question: Would some developer please make wikipublisher aware of the $_GET['userlang'] in order to deal with multiple language wikis?
But I'm just a tinkerer and I do not have oversight over the inner workings.
It is not the role of Wikipublisher to encode support for recipes in the pmwiki cookbook. This is best provided as a separate local customisation or Cookbook recipe. Like pmwiki, the Wikipublisher library is designed so that it does not need to be modified under most circumstances. In the above example, it should not be necessary to change wikipublisher.php; it should be possible to put the same statement in local/config.php.
Since the multilanguage recipe controls $userlang, it may be better to change this recipe so that it sets $GLOBALS['userlang'] if $_GET['userlang'] is set. The recipe already includes this check to set $userlang.