LibMSP is an extremely small public domain embeddable library that WoW RP addons can embed to make supporting the Mary Sue Protocol (MSP) very easy. It supports all the backend protocol internals, and lets you get on with the UI and frontend.
MyRolePlay is based on this library (from 126.96.36.199 onwards); any other AddOns that wish to be compatible are encouraged to use it as well, as it provides a convenient, well-tested, ready-made avenue for MSP support.
However, a user shouldn't load more than one MSP AddOn (whether LibMSP-based or otherwise) at a time, otherwise there could be a fight as to which AddOn gets to implement what, or which AddOn manages the flags.
LibMSP requires WoW 4.1 or later. Its only dependency is ChatThrottleLib (v22 or later), which has no other dependencies.
For more information about MSP please see http://moonshyne.org/msp/