I do apologize about the poor installation process. The first-light engine doesn't yet have a decent means to produce an executable although that is a very soon planned feature. Thank you for trying it!
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It seems you have a previously checked out copy of first-light in your local-projects. If you temporarily move that to /tmp, then reregister the local projects it'll likely work. When there are two identical systems in local-projects, sbcl (and most other CLs) will get confused about which one to run. After you play the example, you can mv the original back.