Starting from STAAD.Pro V8i SELECTseries 5 (build 20.07.10.41), you do not need to check out design codes anymore. STAAD.Pro now utilizes Bentley's Trust Licensing as most other Bentley's programs do. This means that you can use any design codes now even without having a license for it. When you will run the analysis (including the selected design code) a usage data will be sent to the SELECTserver periodically for billing at a later time for your convenience.
You can find much more information about Trust Licensing in the following Be Communities posts:
Changes to Licensing in STAAD.Pro V8i SS5 - Part 1, Trust Licensing
About trust licensing
Trust licensing basics
Understanding, Monitoring and Managing Usages