verb, to sell (something) one has previously bought. Reseller, (noun).
Resale: the act of selling again. Resalable,* (adjective).*
Rights: noun, any claim, title, etc, that is morally just or legally granted as allowable or due to a person.
In our opinion, and for most Internet marketers, Resale Rights and Resell Rights mean the exact same thing, both terms are a common Internet term that has been used for years, so you may find us using both terms here at The MRR Membership . 
There are some that will point to the Dictionary definitions as above, but in the Internet marketing arena (Which is important) Resale Rights and Resell Rights are identical.  WSO's and even the great resell rights marketers use either term, and it's highly unlikely that will ever change.