It would be absurd to me if the same application is somehow allowed via ACP but not via official SDK. Though perhaps the official SDK offers data/features that they don't want you to use for certain scenarios? If that were they case though it would be nice if they actually published a per-SDK-API restrictions list.
That we're having to guess at this feels painful.
edit: Hah, hilariously you're still using the SDK even if you use ACP, since Claude doesn't have ACP support i believe? https://github.com/agentclientprotocol/claude-agent-acp
The only rename I'm aware of is Claude Code SDK becomimg Claude Agent SDK, but that was still seperate from ACP