Can I resell licenses?
Yes, but also no.
What you're allowed to do is pass on the cost of a license to the client that ends up using our product/service. So if you're building a MODX site for a client, it's only logical that you would include a line-item (or incorporate the cost in a fixed fee) on the invoice to your client to ensure you're reimbursed for that. Time you spend implementing our products/services is of course also fair game.
What you're not allowed to do is reselling licenses "as the product". That means you're not allowed to create your own webshop that sells ContentBlocks licenses, for example.
If you built an implementation of our products (e.g. a Commerce theme or Redactor configuration), you may distribute that (free or paid), but you may not embed or otherwise redistribute the product itself, or allow automatic installation against licenses purchased in your own name. You'll need to instruct your users where to buy the product (i.e. the modmore site) from their own account; you may use an affiliate link when doing so.