Originally Posted by you
I used spokecalc and wasn't sure if the spokes should be the same length or not, I also noticed that the only rim dimension taken into account is the effective rim diameter not how the rim is dished or whatever. I am using the Aerohead OCs.
If you look on the "rims" page, you will see that there are two columns that are tinted yellow. These are the variables. The first one is "E.R.D." (effective rim diameter) and the second is "OSB, mm". You should notice that the entry in OSB for the Aerohead OCs is 4.0mm. Look at the rest of the rims and you will see that they are almost all 0.0mm, except for some Ritchey, Bontrager, and a couple of others. Any rim that has an entry other than zero is assymmetric.
So, are they different lengths? I'd guess that they are 1mm different. Most rear wheels have spokes that are 2mm different from drive side to non-drive side.