The best option for a gift is to purchase the boxed version of Photomatix Pro 6 from Amazon.com
Update 11 January 2018: Note that Amazon hasn't yet updated the product name to Photomatix Pro 6, but we expect them to do it soon.
If you are in the UK or close to it, you can purchase it from Amazon.co.uk once the Photomatix Pro 6 items are available, which we expect to be in February 2018.
Note regarding the Amazon page:
Be aware of 'Open Box' Photomatix Pro items listed on Amazon. The Photomatix Pro physical product is delivered in a box with a printed user manual. If it comes without a box, it is a counterfeit, containing a cracked serial number sold by fraudulent sellers.
If you check that the seller is "HDRsoft Ltd", you can be sure you will get the genuine product.
Notes regarding the boxed package:
A back-up CD for our software is not necessary, given that you will always be able to download Photomatix Pro from the download page of our website.
When you need to install the software again, it is better to download the latest version of Photomatix Pro from our website rather than use a version on a CD which would then most likely be outdated. If you prefer to have the software on a CD, you can burn it on a CD yourself, which will spare you handling and shipping costs.
You do not need to buy a CD to install Photomatix Pro on a computer not connected to the Internet. This FAQ explains how to install Photomatix Pro to your offline computer without a CD.
Also, a CD would not enable you to upgrade to a new version. To take advantage of the free upgrades you are granted to (for at least two years after purchase), you would still have to install the software on your offline computer as detailed in the FAQ. Another advantage is that you will not have to wait that the CD arrives to use Photomatix Pro.