No, the plugin doesn't do any checking to see if it is already loaded but that doesn't mean it couldn't. I'll look into that. Even if Validation is disabled, jQuery Validate is also used for CAPTCHA.
If you don't use either Validation or CAPTCH, technically there is no need to enqueue jQuery Validate although that can vary from form to form. The jQuery Validate script is enqueued at the plugin level very early in the process as opposed to at the form instance level. It might be possible to remove it from the queue however I don't think there is a way to determine that it isn't needed by another plugin so removing it from the queue might be problematic.
I'll have to think about it.