Hi Sarah,
No need for apologies. The links you provided can certainly cause some confusion. If you look at a more recent developer guide, its clear which version of Crystal supports Restful.
http://help.sap.com/businessobject/product_guides/sbo41/en/sbo41sp3_cr_restws_en.pdf
Check the bottom of page 4.
Crystal Reports consumes data, so the way I see it is that the Compass API needs to expose data so you can consume it remotely. If their APIs does this, then you can retrieve the data in a JSON format, transform it to XML and use Crystal Reports to report off of the XML (either a dataset in memory or a file saved to disk)
I hope this helps,
Dan