There are three ways to purchase a license for DataGraph, one is through the application, a second is through an on-line store run by kagi, and the third is through Mac App Store.
From the Mac App store:
View DataGraph in App Store
It is a great place to buy DataGraph and get updates. The other methods also include updates, but they are handled through the application and not through the Mac App Store. You can try DataGraph and then purchase it through the Mac App store. The mac app store version also activates the beta version.
From within DataGraph:
Then click on “Enable Full Version”
This brings up a dialog box from Kagi, where you can go to the web store (Buy Online) or enter your credit card information from within the application (Buy Now).
If you buy from within the application, once your credit card has been approved DataGraph is registered and you can print, copy figures, export graphs etc. You will also get a registration key in the mail in case you need it later. If you see your name, e-mail and registration key in the About window, it means that DataGraph is registered.
You can purchase a license for DataGraph through the on-line store as well. You will get an e-mail just like when you buy through the application, but you need to copy-paste the registration key:
The on-line store allows you to use more payment modes, such as PayPal, a purchase order etc.
Question regarding pricing:
At this time there is no special educational price, which avoids having to ask for proof of affiliation. The price is $90 dollars per copy. If you buy multiple copies, you need to do that through the web site. If you buy multiple copies, you will be contacted by e-mail and asked to give the name and e-mail of the additional users you are buying the copies for. Those users will then be e-mailed their registration codes. There is a discount for multiple copies, in that for every 5 copies you buy you get an extra copy. So buy five copies on the web site, and you get six registration codes (includes the one you used to make the purchase).