If I try to access the FTGL wiki at https://sourceforge.net/apps/mediawiki/ftgl/ without being logged in to SourceForge, I get a login prompt.
I would expect the wiki to be public (at least for viewing), not private to SourceForge users only. Maybe this is a configuration mistake?
The problem is due to how Sourceforge has the mediawiki app integrated with their services. To make that URL work without logging in would likely require a trouble ticket to Sourceforge. Instead, I just made the main page link to a different URL that bypasses the authentication attempt.
Thanks for the report.