Bob Smith of Sudley Place Software has released the source code of 386MAX and related tools under the GPLv3 license! 386MAX is a computer memory manager for DOS, and has two neat features: 1. 386MAX supports the Global EMM Import Specification (GEMMIS), which allows Windows 3.x to start in 386 Enhanced mode, even when the EMM manager is loaded. 2. 386MAX supports the same I/O port trapping API through INT 2fh that EMM386 provides. This (at least in theory) should make it compatible with certain emulation TSRs such as SoftMPU and VSB. The code is available at 386MAX GitHub. Thanks Bob!
You also might be interested in other tools from Sudley Place Software, including: a Protected Mode debugger called 386SWAT; a linker called QLINK written specifically to link 386SWAT because none of the available linkers could do the job; a standalone DPMI 1.0 Host called DPMIONE; and various other tools. 386SWAT, QLINK, and DPMIONE are also under the GNU GPL; links point to Bob's projects on GitHub.