This was my screensaver for several years starting in maybe 2001. It felt really cool as a 12 year old to be contributing to the project in some small way.
For a long time I would periodically check on the screen saver in case there would be some big message saying my computer found aliens or something. Never did though :)
My dad did a similar thing with a bunch of computers at his store. It made way more sense back when processors didn't clock down efficiently so there was such a thing as 'wasted/excess clock cycles' you could donate to a distributed computing project. Now though processors shut off cores, reduce their clock speed etc so there's a lot less spare processing power you can siphon off without increasing power draw.
It was my screensaver too and it felt like the most sci-fi thing ever. I'd stare it while daydreaming about aliens.
I remember seeing a prank program years ago that showed the SETI@home screensaver for a bit, then popped up an alert box saying "Alien Life Found!" with options to submit or cancel(!).
If you tried to submit it would spend a while with a really slow progress bar, and then say it failed to submit and asked you to contact SETI directly. I wonder if anyone actually did....