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Installed it, ran it "out-of-the-box", (except for checking file ownership and permissions), and it worked fine up until I wanted to view a user's profile, and commenting out the block of code mentioned above fixed that. No help, I know, but at least you can know that it does work ... sometimes
That block of code doesn't work because the function moduleExists doesn't exist as part of the XoopsModule object in the version of XOOPS you're using.
It's not important, it's just a nice bit of cross-module scripting; if you have the directfriends module installed this will (a little further down in the view.php script) create a link to the addfriend page in the directfriends module, automatically inserting the user id in the form on that page. The module will live just fine without it.
You don't have to delete it, just surround the whole block with /* */ multiline comment tags. Maybe someday you'll want to fix it and use it.
There are a LOT of notices involving the various variables and constant definitions, I'll see if I can figure out what's causing them and clear them out.