This verse speaks of service through desire, not through bondage. If we see God as manifested through humanity, as Jesus demonstrated for us, then the natural continuation of the idea of being in service to God is to be in service to one another. And indeed it is on this idea that society stands. Conversely, it is when we forget this, enslave one another, demand obedience, or deny help when it is needed that our societies become fragile, and begin to crack. The psalmist here acknowledges he is unbound, and chooses to remain in service. The verses around this one, making up the whole of Psalm 116, acknowledge the great gift the psalmist receives through this desire to serve. We are the beneficiaries of the service we perform for others.