There may be some confusion regarding royalties (which I believe may cover one time payments) vs. a royalty interest. Also, wasn't there something in a past statement(s) where PTSC said that we want lump sum payments? Corrections welcome.

Royalties (sometimes, running royalties, or private sector taxes) are usage-based payments made by one party (the "licensee") and another (the "licensor") for ongoing use of an asset, sometimes an intellectual property (IP). Royalties are typically agreed upon as a percentage of gross or net revenues derived from the use of an asset or a fixed price per unit sold of an item of such.[1][2][3][4][5][6][7] but there are also other modes and metrics of compensation. A royalty interest is the right to collect a stream of future royalty payments, often used in the oil industry and music industry to describe a percentage ownership of future production or revenues from a given leasehold, which may be divested from the original owner of the asset.[8]

http://www.enotes.com/topic/Royalties