Developer’s License:

You can do:
The developer’s license means that you are allowed:
– to modify and use the plugin in any custom project (up to 5 projects) for a client;
– you are entitled to get all the plugin updates for the period of 12 months from the date of the purchase. After 12 month period, you can prolong the license.

You can’t do:
– distribute it for free
– resell it

Unlimited License:

You can do:
The unlimited license means that you are allowed:
– to modify and use the plugin in any custom project for a client
– use it in the WordPress themes development with the right to sell themes on the marketplaces for unlimited number of times
– you are entitled to get all the plugin updates for the period of 12 months from the date of the purchase. After 12 month period, you can prolong the license.

You can’t do:
– distribute it for free
– resell it