Jagex's official T&S tells us the full story already:
"You agree that when you obtain your Virtual Currencies and/or Micro-Game Credits from us or our authorized partners, you receive a
personal, limited, non-transferable
, non-sub-licensable, non-exclusive, revocable license to access and select the rights and entitlements that Jagex expressly makes available to you associated with such Virtual Currencies and/or Micros-Game Credits and only in respect of the applicable Jagex Product. The Virtual Currencies and/or Micro-Game Credits are licensed to you and not sold. Any license granted is subject to your strict compliance with these Terms."
TH key is a virtual currency, so it is designed to be
personal, limited, and non-transferable.
Good morning, good afternoon, goodbye. Game, set, match. End of discussion for this thread.