From what I understand (the author told me this) is you can just download the latest and use the same serial number.  However just go to his site directly and ask.  I am hoping he releases a 7 when the SDK's are released.  I have purchased it but I haven't gotten around to installing it yet.

His site is http://www.des-web.net/html/shoestring_shaders.html  real nice guy.

He also has some samples  and other things on his site.  Hopefully he reads this and can post.

Thanks bwtr for that link too.