I don't think there is anyway to remove the Attic files (and thus complete subdirectories) save for having the adminsters of sourceforge do it. This is probably reasonable to ask them to clear out the top level yoyodyne directories, but probably is not that feasible for minor subdirectories. However, for the most part, this should not make any difference. Yes, if you browse CVS via their web interface, you see all that cruft, but if you do a checkout, I'm pretty sure that stuff won't show up.