At the moment the only version
that is available for you to purchase is QME 3.0 which is
compatible with Quake 1.
Buying this version will allow you to upgrade to QME 3.1 preview 2 which is compatible with Quake 2 and Hexen 2.
You can either order QME 3.0 on-line with your credit card, or you can download a registration program that will allow you to order it by paying cash or by writing out a cheque.
Order QME online secure
Order QME online non-secure
Download QME registration utility
After purchasing version 3.0 you can upgrade for free to the preview 2 version.