[15.12] Where can I get the XObject Developers' Kits for Mac and Windows?

For Windows it's easy : the XObject Developers' Kit ships with Director for Windows. If it isn't already installed on your machine, run another custom install with the DfW installer program, and make sure to check the appropriate box.

The Macintosh XDK is supposed to be being revamped, but in the meantime it is available direct from Macromedia for US$50. Many people (myself included) have complained that this woefully inadequate and antiquated product is well past it's use-by date, but you can't really write an XObject without it.

If you have version 1.1 of the XDK, be sure to update it to version 1.2 with the updater available online (it should be on the Direct-L ftp site, ftp://ftp.sharedcast.com/pub/), or see the bugfixes in 15.10 above.