Hi David,
When EV 6 was released that was the last release where the general API's were produced, since then there's a licensable option for EV. The SDK/API's change at each major release so the EV 6 wouldn't completely apply to 7, nor to 2007 as new ones come and others are enhanced. With 6 the PDF was quite small, compared to the almost 200 ++ plus doco now.
Best bet is to have a word with your Sales / reseller person as there are different levels to what is possible. Technology Partners have to be in the STEP (Symantec Technology Enabled Partner Programme) but licensing for end-users is something Sales can best help you with.