M1 is built from a conglomeration of components picked from many versions of MAME plus a unique core that provides some MAME-like services (scheduling and timers, primarily).
For that reason, the current codebase is not very maintainable; the plan is to pick a time when I believe that MAME's architecture is at a reasonable, unlikely to radically change again, spot and then I'll rebuild M1 from modern MAME components.
As far as OSS, I had no idea it would go away as quickly as it did.
The good news is nothing really changed about the source at all in the first place.
Boards was changed to includes and the stuff inside it changed from c's to h's in code extensions.
Some M1 used folders were moved to third party as well and a ton of new sound code folders have been added to it from the MESS side.
Also there are now a load of xml files already made for us which the M1.xml could be changed to direct to the paths for those now so every game added to those files would work instead of people farting about adding games to M1.xml now in turn making every game with working audio in the new system being able to run.
I've rebuilt the trees for you the programmer so we could get something started on both the Windows (FX) and Mac (Normal) native ports of it.
I know nothing about coding myself though so I couldn't get the trees working if I wanted to but to get them there is a good start and I was glad to be of a help making the concept trees to make your great idea come to life as I was dreaming for this new version myself as well and I've had the passion there to build the source trees myself ready made to get us started.
It was your post here that pushed me to make all those posts about making it happen and you really did put the passion into me into helping you archeiving it by making a workable looking tree that you can work with Richard and I do beleive you can make it happen now that we know the new paths for the codes which will hopefully carry on in every new version from now on.
I think this new day in M1 history is going to rock and I for one can't wait to see if you can get our vision working with my trees or a tree of code of your own.
The next couple of months or so is going to be very interesting if you can pull our combined visions off Sir Richard including the 7zip support as I now crave that happening too now that someone brought it up.
Megadrive and Arcade support will definitely both be better than it was ever in the old one has not so much all m1.xml format too as it would attempt to run anything we throw at it now with the multi .xml format with the m1.xml telling the program the paths to the seperate .xmls this time round in my idea for it.
Maybe I have a bit too much passion in the project kickstarted by this post which wowed me too much into wanting it to happen right now. I should be quiet for a little while and wait to see what his wisdom can do with thee new code.