From what I can understand, Raiders of R’lyeh: Horror Adventure RPG and Mythos Sandbox is built off of the Mongoose RuneQuest Rules, which are OGL. Which means, this project shares a gaming lineage and probably high compatibility with Call of Cthulhu. Not that they claim compatibility, as that would probably require a license
That much I can follow. Here's where it gets confusing -
There is a "Black and White" version of the rules that comes in a single PDF (and at certain pledge levels as a Print version, not just PDF) and a color version that splits the PDF into GM and Players books.
The PRINT EDITION (RAIDERS OF R’LYEH IN GOTHIC BLACK & WHITE) is designed for players who want ALL of the rules in one convenient & beautiful tome. NEW: NOW UPGRADED TO A HARDCOVER WITH SMYTH SEWN BINDING.But it's NOT all of the rules. They say so themselves:
Coming in at about 256 pages, it's a good size, but has a significantly smaller page count than the combined player's guide (140 pages) and GM guide (240 pages). I doubt they added 100+ pages of art to the color version. Admittedly, there could be some overlap, but it isn't explained if that is so. The color version is only in PDF, no print option.
Now, they offer the color version as a split of the core rules so players and GMs can have access to what is applicable to them, but without a print option for the color PDFs, the reality is, at the game table, 90% of folks will opt for the printed version. A split of the rules in B&W would have been a nice option.
Also, it appears they've hit stretch goals while still waiting to hit their funding goal (they will fund before it ends in 3 days).
In any case, I have three days to decide wether or not to pull the trigger on this one. I'm on the fence on this, as there seems to be some confusion as to the print version being a complete set of the rules or not.