FYI
As far as I know, ATutor is the only open source system that can be used to author then export content packages, thus allow you to get your content out of ATutor if you decide to move to another system, or to archive standards conformant content in a repository.
There's also Reload, which is an open source authoring tool, rather than an LMS/LCMS. We do recommend using Reload as an alternative authoring tool for ATutor. Reload and ATutor content packages are compatible. The Reload SCORM player can be made available with ATutor if you want to allow students to play SCOs.
http://www.reload.ac.uk/editor.html
http://www.reload.ac.uk/scormplayer.html
There are a couple other open source systems that now have a SCO player included, which allows you to import prefabricated SCOs and content packages from other systems and play (view) them, but you are still essentially locked in since it is not possible yet to get your content out if you decide to move to another system.
There are lots of commercial systems available that supposedly allow one to export content, but given the relative newness of portable content standards, few are doing it right. I won't mention any names, but some systems include propriatary modification to packages which break the standardized format, thus making exported packages only compatible with the system they were created in (After all, letting users migrate to another system would be bad for business. )
Perhaps some day all systems will conform with the standards (as ATutor and Reload currently do), but that is probably still a few years off. SCORM RTE is in the plans for ATutor (i.e. a SCO authoring tool/player), but that's still at least a couple development cycle away, as ADL fixes some of the flaws in the SCORM standard (we can not currently implement full SCORM compliance because the specification does not comply with international accessibility standards) .
You might also want to look into the TILE repository another project by the ATRC. It too in conformant with content packaging and accessibility standards, and is available as a Web service for ATutor, allowing ATutor users to store and retrieve content packages in a central repository.
http://inclusivelearning.ca