No, the equipment that you are running doesn't have to be made by NI. Labview supports anything out there, but you may be on your own for drivers. Sometimes, someone has programmed the drivers for your device already. They are usually posted in the drivers page. You can use those driver programs as the start of your code, putting them where you want them.
Example; I have a Keithley 195 DMM that I want to program for. I search 'Keithley 195 DMM drivers' on ni.com. I get
http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=146
so I sign in and download the drivers. It really takes the pain out of programming the com commands or the GPIB protocols when you have a starting point like this. Older or more fringe equipment may not have the drivers, in which case, good luck!
Most labview coding, at least in research fields, is done on non-NI equipment. NI has given us a very flexible base to use with a huge number of pieces of equipment, which is why we stick with labview and NI, even if we can't use their equipment.
