Being charged with visa fraud for working on a B-1 for business is unlikely, because the legalese is fuzzy, difficult to read (if you are not a lawyer) and rarely, if ever, explained to the visa holder.  Thousands of such cases are known to occur each year, without any effort made to enforce.  Also, the statute of limitations would have expired anyways.

On a more interesting note, Michael Wildes, an immigration attorney who worked for the Trump Organization, told Univision that Melania Trump obtained a green card in 2001, “based on marriage.”  Given that she married Donald Trump in 2005, and also claims that she was never previously married, this would imply to any conspiracy theoriest that she used the fiance green card trick to gain permanent US residency, without actually intending to remain married - which is illegal and could result in losing her US citizenship, as well as being deported, even today.  In which case, she has good reason to NOT reveal her immigration paper work.