Make note that this isn't Old School RuneScape, a version that's based off a build of 2007. It's available on iOS and Android since the year 2018. This is the full-blown RuneScape that Jagex is constantly making improvements to RS Gold over the past 20 years.
There's no doubt that there's a demand for RuneScape on iOS or Android. The game has more than 1.8 million players pre-registered for these versions, which offer a mobile-friendly user experience that has been revamped with new menus, icons, text and textures. Combat mechanics are also adjusted for iOS in addition to Android.
The company has filed two trademarks in the UK One trademark is to "OSRS Gold" and the other with the title "RS Gold" The filing noting that it has registered the use of the phrases as words. This should stop third-party sites from being allowed to claim that they sell RS Gold.
A quick Google search for either of these terms brings up hundreds of websites, majority of them with one of the words in their URLs. Many of them offer currency in RuneScape as a substitute for real money. This was in response to the announcement on the 13th of October that Jagex announced that it was ending the practice of "real-world trade". On its blog "The RuneScape Team" clarified that "gold obtained through RWT real-world trading is a concern in buying rs account any online game featuring a tradeable currency."