31 years after I started programming WHAT IF, working conditions made me retire. And with it retired WHAT IF. So, there are no distributions any longer. But.... Elmar Krieger to the rescue....
Since 2007, WHAT IF has been available as a joint distribution with YASARA called The Twinset.
There are four stages of YASARA, each providing additional functions:
http://www.yasara.org/products
WHAT IF can be bundled with all four YASARA stages. The fanciest is the YASARA Structure/WHAT IF Twinset, which includes MD simulations, advanced homology modeling and docking. Since YASARA development is financed by its users, the upper YASARA stages come with a price tag of a 100-400 USD/EUR for single academic users.
If paying for YASARA is not an option, then you can still use WHAT IF in the free YASARA View, which has however only limited functionality compared to the non-free YASARA stages.
Note that the Twinset is available for Linux and 64bit Windows, but not for MacOSX and 32bit Windows
The main aim of WHAT IF distribution always was that the program can help you do science. And with the YASARA twinset that is no different. We spent a lot of time making the programs distributable for this purpose only. And in the case of the YASARA Twinset that is very, very remarkable because Elmar Krieger runs the YASARA company to pay his bills, he is not paid from a grant or anything. The most holy rule for WHAT IF users always was that they should properly acknowledge WHAT IF or its derivatives:
1. WHAT IF reference:
WHAT IF: A molecular modeling and drug design program.
G.Vriend,
J. Mol. Graph. (1990) 8, 52-56.
2. WHAT_CHECK reference:
Errors in protein structures.
R.W.W. Hooft, G. Vriend, C. Sander, E.E. Abola,
Nature (1996) 381, 272-272.
3. YASARA Twinset reference:
YASARA View - molecular graphics for all devices - from smartphones to workstations.
Krieger E, Vriend G.
Bioinformatics (2014) 30(20), 2981-2982.
And there is more. You are not allowed to (re-)distribute the programs; neither for free, not for money. You can also not take parts of the program and use them in other programs (an exception is made for WHAT IF subroutines that have their name start with GVS or GVF, those can be 'stolen' and distributed as much as you want, as long as proper acknoledgements are made). Feel free to make your version accessible to other scientists (but only on your computer). We want people to obtain WHAT IF or the YASARA twinset in a way that they realise where it came from and know with head and hearth that we need citations.
And perhaps, send Elmar a nice mail thanking him for doing what no other company ever did, doing work for you, for free...