Charts from BMS Mirage were used in DCS Mirage manual, with the permission from creators of those charts. From what RAZBAM said, they have used additional material, other charts, pilot input etc in development. Flight model is still in development, and entirely complete. But it isn’t really a copy paste of BMS model.
As to accuracy of Mirage’s flight performance in BMS, I’m sure there are people much more in the know about subject here than I am, but last I heard, acceleration and turn rates etc were quite accurate but the aicraft still used F-16 FLCS therefore flies differently from Mirage. While not up to the degree of F-16, there still has been a good deal of research and development for Mirage 2000 in BMS as far as I know. You can check in documents folder of BMS installation, some docs about Mirage FM under “docs/other documentation/flight models” folder. For DCS Mirage 2000, RAZBAM developed a new FLCS, from available accounts and pilots, to construct an FLCS code. It is not from released information or directly code itself for real life platform like F-16 FLCS in BMS, but with French being so stringy with classification of such stuff, RAZBAM took the best approach they can to model a plausible rendition of FLCS for a Mirage.
There are other stuff in Mirage module that needs completion, but flight model is not much to complain about so far, from my experience. Although, I am not entirely knowledgable about all the intricacies of Mirage 2000, but people who are die hard Mirage fans seem to be generally happy with flight model. Other stuff are being fixed fairly rapidly.
I also somewhat question “if an aircraft has so much classified stuff, should it even be done?” but, a lot of people wants the newest aircraft they can get, and there are very few 4th gen aircraft one can do without having to guesstimate some bits, so I guess more of such modules will come. I have bought Mirage out of curiosity and to give a chance to RAZBAM. I had reservations, but overall I can’t say I have been disappointed, even though there are quite a bit more stuff to complete in module currently.
Long in short, if you want a really complete product, you better wait on it. If your only reservation is that flight model is not well researched and just copied from another source, that is not really an accurate statement. Though, that is not to mean it flies exactly like a Mirage 2000C, since that is not something I can either confirm or deny as I didn’t fly a real thing :). If, you really like the aircraft itself, and want a depiction of it as as real is currently possible with available data, both in avionics and flight model wise, module is the best you can get currently.
Also, be mindful that it is a fairly early version of Mirage 2000, from about mid 80s, and not quite the multirole monster F-16C we have in BMS. No active radar missiles, or air to ground missiles on this variant of Mirage.
My personal stance was to hold off on getting the module until I was sure it is worth. But, in a lapse of reason, I got excited and got it anyway, especially due to they did release it with a AFM, as opposed to integrate it later on. Although there are quite a bit of things to complete on it’s systems, and flight model itself is also getting updates, I personally think it is enjoyable in it’s current state, but that’s just me anyway. And waiting on it a bit, as my original line of thought was, can still be considered the more reasonable choice.