To me this sounds pretty clear:
“FOR COMMERCIAL USE” LICENSE DETAILS
By purchasing a “Commercial Use License” on Fiverr, the seller grants you a perpetual, exclusive, non-transferable, worldwide license to use the purchased delivery for Permitted Commercial Purposes. Unless clearly stated otherwise on the seller’s Gig page/description, all intellectual property rights of the purchased delivery are hereby assigned to you.
I see the possible pitfalls more along the line of what jelsinardaooo says, and you can find lots of related posts on the forum if you search, there are a lot of sellers who either don´t have the slightest idea about IP, copyright and such, or ignore it. If you find a seller you can trust on that, you shouldn´t have problems in that regard, else, better not rely on your license being worth anything.