phpBB 3.1.x extension adding EVE Online SSO / OAuth2 authentication your forum, allowing you to securely log in to the forum with your EVE Online account.
Copy the folder phpbb-ext-evesso into your ext/cyerus directory in phpbb's root (You will need to create cyerus manually). Rename phpbb-ext-evesso to evesso, leaving you with ext/cyerus/evesso.
The extensions should now show up in your extension management (ACP -> Customize -> Manage Extensions) to be enabled.