What's the point in supporting ReactOS?
It's free. So what? Maintenance costs would eat benifits.
It's Open Source. So what? Who's gonna read your sources?
What can you really offer, what real benifits it provides?
You can get some interest if you offer some enhancements over MS.
Better customization and user control.
2003-style desktop with 2008 features.
Running more than one instance of the OS with hrdware partitioning.
Running 64bit applications on 32bit OS.
Whatever else, which is not possible on MS Windows or requires 3rd party software.
You would be able to say: yes, it's still buggy, not fully compatible, etc., BUT IT CAN DO THIS AND THAT! That would be a selling point! That would attract computer enthusiasts. That would be something people would talk, that would go to the news, etc.
AMD has some special features on their CPUs. They may give you some money if you make use of them in the ROS.
What about asking for money from MS and/or Apple
If I were US president and I heard Putin refused I would give you $$ just on a principal matter.
Another idea: small trade-mark icons of contributors of $10,000 (please don't go below 10 thousands) would be placed on ROS login screen for 5 years (permanently if over $100,000).