FL Studio can also be used as a VST instrument in other audio workstation programs and also functions as a ReWire client. Image-Line also offers other VST instruments and audio applications. FL Studio is used by hip hop and electronic musicians and DJs such as Afrojack, Avicii, Boi-1da, Seven Lions, 9th Wonder, Metro Boomin and Southside, as well as Dyro, Madeon, Porter Robinson and Martin Garrix.
FL Studio can make custom/composed sparta bases and other music. It can also make sparta remixes and mashups. Tomiato64, GSR, Aduburyus, CloudNinja, and PiaNO! are just few examples of sparta remixers who uses Fl Studio. This program also started Gross Beat, Free Filter, Fake Percs, decent vibrato, and NewTone (FL Studio version of melodyne) in sparta remixes.
Official and legal download: http://www.image-line.com/documents/flstudio.html
Note: the demo is pretty much ok, the only thing you can't do is open .flp files (project files). So no need to pirate (unless if you really want to).