You are correct that the $12 version is not the full source. It is only the portion of the source that is external to the 4coder core, and implements the default custom layer.
The full source is not on sale for download anywhere, but we can discuss a closed source license if you email me at
[email protected]. Also if you want access to the platform stuff to fix a bug or add a feature we can instead discuss that. 4coder is not an open source project, so if you were hoping to use the platform layer as a starting point for your own platform layer, the source is not available in any form for that purpose, but I would be happy to discuss with you the structure and details of the layer to help you implement your own.