First post, by digger
The source code of 386MAX, an alternative to EMM386 and QEMM, has been released under the GPLv3 license.
Back in the DOS days, 386MAX was sold by Qualitas.
386MAX supports GEMMIS, which allows Windows 3.x to launch from DOS in 386 Enhanced Mode, even when the EMM manager is loaded.
Also, it supports the same INT 2fh I/O port trapping API as that of Microsoft's EMM386. Emulation TSRs that depend on that API, such as SoftMPU, should therefore (at least in theory) be able to work with 386MAX as well.
The source code can be found here: https://github.com/sudleyplace/386MAX