The ACLU is not as simple as "defending civil liberties." For example, the right to bear arms is built into the U.S. Constitution, but the ACLU is not anti-gun control. It's not just that that a lot of ACLU members are liberal, but that a liberal ethos (it can be argued) informs ACLU's ideas of what civil liberties are, and its overarching plan of action. Nonetheless, there is a significant number of conservatives who have made peace with this liberal ethos enough to support the organization. They might not embrace the liberal vision which dominates the current ACLU, but they are nonetheless made welcome as full members and allow to affect policy.

Similarly, everyone will be welcomed as OTW members (as I understand it) even if they reservations as to the vision which motivates. It is certainly possible that enough people who don't share the vision will become members as to radically change it from what is now; I don't expect it to happen, but it's not impossible.

Everybody will be allowed to use the archive. Anyone who pays $10 will be a member. At least, that's how it was explained to me.