Yes, it's safe to use, but mods are still wishy-washy on if it's against the rules or not. By that I mean some mods have declared it against, and some have declared it's alright to use. I don't doubt you'll be caught, however...
It's completely safe. Runescape mentioned it awhile ago giving thanks to swifter or whatever who ever created it, but also Jagex has been accepting things like swiftkit etc. They want to see more fan sites also. I read it month or so ago on the forums.