RuneScape is freeing up a lot of names now. The developers announced a while back that old an inactive names would be getting removed from the list soon, and the first batch is due to hit very soon. That means former members who have not logged in for two years and free users who haven't logged in within six months will have their character names dropped back into the pool of available sobriquets.
The upside? Members will have access to a lot of new options for name changes. The first batch will cover names starting with A through C, and Jagex intends to post a page listing the reclaimed names; however, the page will be accurate only at the time of reclamation, with no updates to show what's been taken. So if you're hopeful to finally change your character's name to Arquebus, you'd better be ready.