The Short Version
We've worked really hard to ensure TNT Basic and Hieroglyph are bug free and as stable as possible; however, if either of them suddenly go wrong and they wipe your disk/blow up your computer/trigger an apocalypse we cannot be held responsible.
If you do find any bugs or things which don't seem right, please please please let us know through the community forums or TNT Basic's bug tracker. It would help us even more if you could use the bug reporting scripts that are part of the TNT Basic distribution.
Remember, you are using TNT Basic and Hieroglyph at your own risk - repeat after me "The authors are not responsible if TNT Basic or Hieroglyph do bad things to your computer".
Sorry we had to rub this in your faces, it's the world we live in.
In using this software, you understand and agree that this software is provided as is without warranty of any kind. The entire risk as to the results and performance of using this software lies entirely with you, the user. The authors do not make any warranties, either expressed or implied, including but not limited to implied warranties of merchantability and fitness for a particular purpose, with respect to this software.
In no event shall the authors be liable for any consequential, incidental, or special damages whatsoever (including without limitation damages for loss of critical data, loss of profits, interruption of business, and the like) arising out of the use or inability to use this software.
Although copyrighted, both TNT Basic and Hieroglyph are open source, and can be distributed in accordance to the covering licenses as described here.