You've missed one important paragraph :
<< Entropia is a for-profit corporation. In our view, profit is as necessary as oxygen for longevity; while oxygen is essential for life, it is not the purpose of living. Likewise, Entropia's Internet computing service represents "profit with a purpose." Some of the time, Entropia's software will be running commercial tasks on your computer. >>
In other words, they receive money for CPU power you donate to them freely.
If you want something similar to this (that's actually quite usefull), you can check out folding@home. It's about the best way proteines should form or something along the lines. I don't have an URL ready, but it should be around here somewhere.
We respect your choice of doing fightAIDS@Home, but most of us do this because of stats, races and commerady.