bajan4evr wrote: On how many websites can i install my current CB Subs plan? Do i have to purchase another plan for another website or can i simply upgrade my current plan?

You need an extra license per unique site.
You can either upgrade existing license to add new website to it or you can purchase separate license for new site (so you will be given new license id to use on that site).

I guess purchasing separate license code is more flexible since you can have different user count.