The problem with rainbowfish is they will all hybridise with each other and produce fertile offspring. If the M. boesemani were accidentally or even deliberately crossed with another rainbowfish, you can end up with fish that resemble the original but have slight variations.
I got a male Glossolepis incisus many years ago and it looked like a legitimate fish and came from a reputable shop. A while later it developed a huge anal fin, which the fish should not have had. It turned out to be a hybrid between G. incisus and G. wanamensis, but it looked like a G. incisus for the first year.
If you just want the fish for display purposes, then they are fine. However, if you plan on breeding them, I would probably pass on them.
The safest way to get true species of rainbowfish is to either catch them from the wild (unlikely to happen unless you go to New Guinea), or buy them from a reputable breeder. There are a few rainbowfish societies around the world and some of their members send eggs to people in their country. You might be able to get eggs or fish from the two German sites below.
ANGFA in Australia
The Australian and New Guinea Fishes Association - ANGFA
homepage, dokument, webpage, page, web, netz
There used to be one in America too but I can't find it now. Gary Lange in the USA is someone to look out for if you want rainbowfish over there.