Visiting the site throws up a popup box asking you to register and supply details about who you are and what products you use before you can get a username and password to access the files. If this was an official IBM website I’d have no problems filling in the details but the Lotusphere PDF’s seem to be hosted by a company called IB Systems who just happen to be ‘experts’ in the Domino field.
My guess, they just want your details so they can try sell you services. The site doesn’t have any indication that it’s been authorised by IBM and there should be no reason to request the details that they want.
You can fill in your details if you want but I’ll be steering well clear.