Not only that but what is to stop the person hosting the private runescape server from taking you real runescape account? Nothing! Not only that but they may ask for your email address and or password to that too.
If they ask you to install some "client side software" then that should immediately ring alarm bells.
You'll just be downloading spyware and viruses.
I've personally never used a private runescape server because I've never needed to and I don't want to have my real account stolen.
Please remember to play it safe and just stay as far away from these "runescape private servers" as you possibly can.
There's a VERY good chance that they are just there to steal your account and ruin the game for you, or far worse, hack into your computer and steal your private data, such as usernames, passwords and credit card numbers So if you want to do better at runescape and level up fast, as well as make a ton of money at the same time, you should sign up to my free runescape tips newsletter.
You'll get loads of tips over the next month and you'll also get the special link to a private forum full of other runescape players where you can post and ask as many questions as you link, and learn tons of top secret tips that they use to generate tons of cash.
Sign up now, it's free so you've got nothing to lose.