Can I use Snapshot on more than one website (different hosts)?

Can I use Snapshot for my client's website as well as my own?

My client has a different web host and does not want to move.

My second question is, later next year when I have a couple more domains up and I'm using WP Multisite, again: can I use Snapshot for my clients' websites as well as my own under this one membership?

Or am I allowed only one copy installed of any plugin here?

Thank you!
Jeda