dash is just another shell alternative to bash, like zsh and others. I don't think using it would cause any damage to your system, since in Ubuntu is sort of the default shell when you run scripts with the /bin/sh command (/bin/sh is just a symlink to /bin/dash.)
Since dash is a very lightweight shell, you must specify the bash shell in the script if said script uses any bash feature not available in dash, using a line like this:
as the first line of your script.