As a quick note, this question is being asked in the general sense. As such, it can be a little difficult to give a straight-up answer for every single kit that people will be using. However, as most kits are designed similarly, it probably is not the best idea to expose your cookware to open flames. This is mainly due to their compact size and that the pans could end up warping and changing color as a result. Then, your food would be affected in a negative way, as well.
If an open fire is your only heat source, then you could probably get away with heating your food granted that the fire is kept under control. Sure, it will slow down the process but these kits were generally not designed to withstand excessive flames.