[mthg]

SDL for boilerplate, ODE (Open Dynamics Engine) for the physics. My understanding is that ODE was started by a ex-Havok employee, and it is in fact an excellent oss physics engine.

[bd]

Not Havok, but close. It was MathEngine, which made Karma physics engine (used for example in old Unreal).

They were later bought by Criterion (RenderWare) which was subsequently acquired by Electronic Arts, where it just died.