The idea is they will invest it for you and keep a record of your name. Then in the future when time travel is possible (assuming I suppose that it is not currently possible), they will pay the time travelers to come get you and take you to the future with them.
They explain: "We establish a fund in current time. You make a small contribution to the fund, and in a few hundred years that small amount grows to a very large amount. From that fund, moneys will be taken and used to retrieve you, perhaps seconds after you join, perhaps even moments before your recorded death, perhaps some other point in your lifetime."
Anyway, check out the webpage and decide for yourself if you are willing to invest in the Time Travel Fund (TM). That page should answer all your questions. Questions such as "are there any restrictions?", and "what if they outlaw time travel?" (interesting question), and "is this a joke, scam or cult?"
It's an interesting idea.