Is the OpenAI Agents SDK open source?

Yes. Both of OpenAI’s own packages, openai-agents-python and openai-agents-js, ship under the MIT license, so the SDK’s source is public, modifiable, and redistributable without asking OpenAI first. That covers the wrapper only: the loop, handoffs, guardrails, and tracing the SDK adds on top of a model call. What the loop calls, OpenAI’s models through the Responses API, is unaffected by the license on the code that calls it; running an agent still bills like any other OpenAI usage, open source or not. The Claude Agent SDK’s own license story is only half the same: its Python package is MIT-licensed too, but its TypeScript package is all rights reserved under Anthropic’s commercial terms, a per-language split this SDK doesn’t have. Either way, reading or changing the wrapper’s source doesn’t change what running it costs.