Leaked version 0.3? SA-MP Source Code

[Giga]

There is no known existence of a leaked SA-MP 0.3 source code if I recall correctly. If you are referring to OpenMP making use of leaked SA-MP source code, then no. I can vouch for the fact that several members of the development team are smart enough to create their own modification without replicating any kind of external code. All it takes is knowledge and skill to exploit the base game (in this case ? GTA: San Andreas) to create a game modification.