Which version of Billboard are you using? How many lines of text do you want to display? There's a hard limit of possible lines in order to avoid screen burn in.
Yes, the script is invoked with a 1000ms time limit in order to avoid "hangs" by badly coded scripts. Output is captured from stdout.
Caching the data is actually a good idea, and you should do that in general (e.g. also in cases where there is no internet connection). Also saves battery power.