Can the Mavericks install binary be shared between two different apple accounts?
Yes, you can reuse the downloaded installer across Macs, even if they're using a different Apple ID account for The App Store. The installer contains nothing in it that prevents it from being used this way.

Data about App Store accounts comes from existing user data on the machine during the upgrade, it's not embedded in the downloaded installer.

The legalities of doing this seem fine: the upgrade is free and the user is required to accept the EULA when they run the installer application, before the install begins, so you're not bypassing some acceptance of this agreement by sharing the installer instead of downloading it from the App Store.

Edit and field test: A friend used my pre-downloaded copy of the installer on his MacBook Pro tonight and it worked just fine.