Q: Can I subscribe 1 Sku Grid account for multiple marketplaces?
A: Yes, you can use any subscription you want for as many different marketplaces as you want... however, for each marketplace, there can only be 1 account in sku grid.
For example, if you have 1 eBay account that lists to various countries, that would be fine. But if it's 2 different eBay accounts, you'd need to run 2 different sku grid accounts.
Likewise, if you have 1 eBay account and 1 amazon account, that would be fine.