It seems odd to post this on the forum, but searching the Adobe site to report it referred me here...
The link to download the Illustrator CS6 SDK at Adobe Illustrator SDKs | Adobe Developer Connection is broken, leading to a 404 page. The other links all seem to work.
The initial URL is now redirected to the URL provided by @LeoTaro , which centralizes the links to download the script resources for all versions, but the URL to download the CS6 SDK is down. I have tried several times over the past 3 or 4 weeks. I also tried on console.adobe.io where the CS6 version is not listed at all for all resources.
Does someone would be kind enough to upload the CS6 SDK archive for me? Because I don't even dare to hope the link can be fixed someday.
After a few hours fiddling with a custom script (to round path points), with the ExtendScript Toolkit, and reading a few resources here and there, I think I might not need the SDK archive. Though I'm still confused by some undocumented things like the support for the "const" keyword or a custom "module system", but not of parameter defaults.
(I'm sorry for the consecutive posts)
The full SDK contents are available in C:\Program Files (x86)\Adobe\Adobe Utilities - CS6\ExtendScript Toolkit CS6\SDK
That's good to know. With many apps Adobe have been agressive about closing down SDKs for versions no longer sold. Adobe don't gain sales when developers make plug-ins for CS6. Rather the opposite.