Near as I can tell, this is still from seaweed. Now... whether they use processing methods that are not vegan, I'm not sure.
Here's a geekspeak tech paper written about carrageenan that may or may not help... they don't speak to calcium carrageenan except in a reference at the end. I only scanned it but thought it was still better at explaining generalities of carrageenan than other sites further up the search engine response. http://www.fao.org/docrep/X5822E/x5822e05.htm
Oh... and it so happens that one of the paragraphs toward the end I happened to scan had this sentence which made me crack up:
"Barring political upheavals in the harvesting regions the industry can remain assured of adequate supplies of good quality weed at reasonable prices."
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