Cloud9 and FSDreamTeam are entirely different companies.
Addon Manager is not made by Cloud9, it's made by Virtuali, my company, that owns the FSDreamTeam brand. The relationship between us and Cloud9, is that Cloud9 pays us a license to use our Addon Manager, not viceversa.
Of course, since the program it's the same, and can handle different products from different publishers (FlorenceX, from Aerosoft, use that too), all at the same time, we take care the last versions is always backward compatible with older products in the installers, by always installing all the last version of files that are guaranteed to work with all products/publishers.
You will always have only one version of it installed at any time, exactly like you don't need (for example) multiple versions of FSUIPC, if you have different addons from different developers using it.
So, you don't have to worry about backward compatibility, it's our job to verify this works.
If you install any of our products, the installer will come with all the needed files to support Cloud9 and Aerosoft products. And, if you install any products from these companies that use the Addon Manager as well, file date/version checking in their installer (even if older than ours), will prevent an older installer to overwrite newer files coming from a newer one.
So, basically, you shouldn't worry about compatibility with other products using the Addon Manager and, of course, you can check this before purchasing, by simply installing the Trial for O'Hare.