dos32a

DOS/32A is a free, open-source DOS Extender which can be used as a drop-in replacement for the popular DOS/4GW DOS Extender and compatibles. Being fast, small and flexible DOS/32A can be used in many environments, from embedded systems to DOS emulators, by both developers and end users alike.
Since May 2002 DOS/32A and its source code have been opened to the public. Nowadays the project is being maintained by its original author and, although no active development is currently planned, patches and bug-reports are accepted and reviewed during my spare time.