[DirtyFexen]

It seems possible to crowdfund that amount. Could set up some sort of perpetual sale/donation page on 3D Realms own website that frequently had games packaged together with Steam keys, option to donate, by exclusive merchandise that contributes to that fund.

Do it 3DR!!!

For anyone who does not understand the IP buy-back above it is originally from the 2010 agreement between 3D Realms and Gearbox for the sale of the IP. The wording means that 3DR would have to repay all the money they received from Gearbox in exchange for the IP (sales, publisher advances). The three title thing is a provision for the future, meaning if Gearbox were to do a new Duke game 3DR would have to repay them for whatever profit they got out of it.