Why don't you want to release the source?
why do you want the source to be open?
one could say "security issues", but you have to trust the server-admin anyway, no matter what,
if he wants to cheat, he could change the code at any time, so there's actually no point in releasing the code.
i'm sure there's reasons to ask for it, but if you think about it, it wouldn't change anything,
it would just enable others to create new (and eventually cheating) pools, which is one of slush's reasons not to do it.
if he doesn't want to, that's ok to me, there's no
need to know the code, cuz it wont proove anything anyway.
just my 2coins

There is obviously no need to open the code, I mean, it's not a trust issue, like I want to *check* the code.