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I always shiver when someone asks questions about xoopschat, because these were my first steps porting a module to XOOPS 2 (quite a disaster). In the current versions of XOOPS there is no xoopsjs.php anymore.
Take an editor and search the module for the word xoopsjs.php and replace with xoops.js. That should do the trick (hope so).
I guess the rest of the warnings you could ignore (hope so again).