In celebration of RuneScape’s 15th birthday, Jagex has once again made the oldest iteration of the game available to the public. Starting today and running through mid-March, players can log in and secure themselves indefinite access to the classic servers with all of their old school glory. Your account from RuneScape won’t transfer over, so if you haven’t played before you’ll be starting over.
The availability of RuneScape Classic is limited to current RuneScape members. If you are a member and wish to take advantage of the open window, head over to the official page and log in with your current RuneScape account from 11 January at 12:00 UTC until 11 March at 12:00 UTC. Once you’ve made a character, you will have access to RuneScape Classic whenever you want to play it.
RuneScape Classic remains online for the remaining community that continue playing as well as players who would like to see how the game looked pre-2004. Due to the ease of cheating, the game is mostly closed off to the public with small windows of time where new players can obtain access. The last time that the servers were open to new players was 2011, at which time Jagex claimed that the game would not be opened to the public again. Whether the current event is a one-off exception is unknown.
(Source: RuneScape)

I actually play this on my Android phone using RSCRevolution. You install that app and then you can play on your phone. You can’t do this with the opening launch of classic so it’s a little bit of a loophole.
Looks good, I am now going to try another one called http://www.rsclegacycom, they say they will have an android version too with additional updates to make it appeal to more people, so we will see how it turns out!