These two products resemble each other only at the very simple level. This, in turn, means two things. Clipper and FlagShip have a lot of C-like features, which I suspect won't be a problem for most Linux users. Their target markets are also different. If you want a program you can run on your desk to keep track of time billed to clients, or that will maintain a data base of customers or your inventory, dBMAN will do the job, but FlagShip might be overkill.
FlagShip is aimed at people who want to develop or port software packages.
These products were evaluated with these criteria in mind. As I mentioned previously, FlagShip is a compiler. It translates the xBASE code into C, and the result is turned over to the gcc compiler. The compiled binaries may be distributed without paying royalties to multisoft. However, there is a public-domain program in WorkGroup Solutions' FTP area named dbu .