I have been able to get a basic jam functionality working for digital mars :) jam-lovers, try it out!  The "actions Link" part will need to be extended if you want to do anything complicated :)

Here is the diff:

190,208d189
< ##########################################
<     else if $(DMCDIR) {
< 	#Echo [WARNING] DMCDIR is set $(DMCDIR) ! ;
< 	AR          ?= $(DMCDIR)\\lib ;
< 	CC          ?= $(DMCDIR)\\bin\\dmc.exe ;
< 	CCFLAGS     ?= "" ;
< 	C++         ?= $(CC) ;
< 	C++FLAGS    ?= $(CCFLAGS) ;
< 	LIBDIR      ?= $(DMCDIR)\\lib ;
< 	LIBFLAGS    ?= "" ;
< 	LINK        ?= $(DMCDIR)\\bin\\link ;
< 	LINKFLAGS   ?= "" ;
< 	LINKLIBS    ?= $(DMCDIR)\\lib\\kernel32.lib ; # $(DMCDIR)\\lib\\oldnames.lib
;
< 	OPTIM       ?= "" ;
< 	RC          ?= "" ;
< 	STDHDRS     ?= $(DMCDIR)\\include ;
< 	UNDEFFLAG   ?= "-u " ;
<     }
< ##########################################
1647c1628
< else if $(NT) && ! $(DMCDIR)
---
> else if $(NT)
1882,1908c1863
< if $(NT) && $(DMCDIR)
< {
< 	actions updated together piecemeal Archive
< 	{
< 	if exist $(<) set _$(<:B)_=$(<)
< 	$(AR) /out:$(<) %_$(<:B)_% $(>)
< 	}
<
< 	#actions As { $(AS) /Ml /p /v /w2 $(>) $(<) ,nul,nul; } # ANUJ: assembler for
dmc?
<
< 	actions Cc
< 	{
< 	$(CC) -c $(CCFLAGS) $(CCDEFS) $(CCHDRS) -I$(STDHDRS) $(>) -o$(<)
< 	}
<
< 	actions C++
< 	{
< 	$(C++) -cpp -c $(C++FLAGS) $(CCDEFS) $(CCHDRS) -I$(STDHDRS) $(>) -o$(<)
< 	}
<
< 	#$(LINK) $(LINKFLAGS) /out:$(<) $(UNDEFS) $(>) $(NEEDLIBS) $(LINKLIBS)
< 	actions Link bind NEEDLIBS
< 	{
< 	$(LINK) $(LINKFLAGS) $(>) , $(<) , $(NEEDLIBS:B) $(LINKLIBS:B) /noi
< 	}
< }
< else if $(NT) && $(MSVCNT)
---
> if $(NT) && $(MSVCNT)