EZGUI seems to run under ReactOS as far as I can tell with my limited testing.
There is a reason for this. I mentioned this before, but I will reiterate it again. While EZGUI is feature rich, I chose not to lean towards the "leading edge" of the WIN32 API. Instead I chose to use long existing API's as far back as Windows 95 and simply push them to their limit. One example is my Canvas control. Even its 2D sprite engine should work even on Windows 95, since I use the Windows DIB engine which has been there since the beginning of 32 bit Windows.
Somewhere around Windows XP, a number of API's changed data structures passed to them. EZGUI rather than simply use the latest versions, test the OS to see what version it returns back and if an old version it uses an older data structure and if a newer version is uses a later version. This makes it compatible on a large variety of Windows versions.
Another trick I use for a few later API's is load them dynamically. I use LoadLibrary to see if the OS DLL needed exists (ie. Theme DLL) and then load the DLLs as needed. Then I test the DLL using GetProcAddress to see if the needed API exists. If it does I use it and if it does not, I either use an alternate method to handle the task or simply turn the feature off (ignore it) in the EZGUI runtime.
This is why it does not surprise me that EZGUI runs very well on not only Linux using Wine, but also ReactOS.
A lot of thought and planning went into the development of the EZGUI runtime and backward compatibility was a high priority on y list.