I have asked similar question for Linux RPM (Adding License Agreement in RPM package). Now i have same query for Solaris package. I could not get any helpful link / details
I would implement that using the checkinstall script.
"exit 3" in that script gracefully ends the package installation.
That's not trivial as you need to create a request script and reference it in the checkinstall one.
http://docs.oracle.com/cd/E18752_01/html/817-0406/ch1designpkg-24309.html#ch1designpkg-4