I want to publish some software for different Linux distributions, using the regular Linux packaging formats (rpm, deb, yast, etc). My package will require a click-thru license agreement. Which Linux tools and package formats support a license in the package which is shown to the user before installing the software?
.deb definitely does; the sun-java* packages from Debian non-free have one.
Keep in mind that on Linux (and other Unix systems), often an administrator installs the software, but different people actually use it. You may want to show your click-through license the first time each user runs the software.
(Well, actually, dpkg is text-based, so its not click-through, but rather type-through, but...)