So I found a way to use DubScript on my Kindle HD 10.1 tablet. I'm posting this just in case someone wants to try it. I'm not offering iron-clad guarantees, just noting that it's worked for me so far.
To start with, I used How To Geek's tutorial on how to install the Google Play store on the Amazon Fire tablet (without rooting it). Basically, I downloaded 4 Google Play Store APK Files in order, and then installed them in order. The Google Play Store* icon showed up on the tablet and I signed in in the usual way.
Then I just downloaded DubScript and the other apps I wanted. I started testing Dubscript to make sure it was fully functional. Creating new script files, copying and pasting Fountain files in, editing existing script files and so on. Great, right?
Not really, because DubScript or Kindle or both, would not let me save my files. I tried a variety of ways to get around the problem, but DubScript kept telling me I didn't have the space, or I didn't have permissions, or I didn't have something, whatever it was I needed to save those files.
I played around with it for an hour or so, and then gave up. Oh well. I resigned myself to writing scripts on the Kindle in plain text without DubScript's lovely little interface. But I needed to test that too. Just to make sure I could move the plain text files around from phone to tablet to laptop as needed.
I was using a flash drive connected to my tablet with an OTG cable. With ES File Explorer app, my tablet could access the flash drive just fine.I opened DubScript again, pasted in a plain text Fountain file to see what it looked like in screenplay format. I tried saving again, but this time, DubScript gave me the option of sending the file to the flash drive via ES File Explorer.
I tried some variations on this approach, and it turned out I could save to the flash drive with no problems. I could then attach the flash drive to my Android phone and open the file with DubScript there. I could email the file via gmail to my laptop and import it into Fade In.
So this is one long winded post. (The Aristocrats!) But I'm thrilled because I now have a powerful, portable, multi-platform tool to use in my writing.
*Once you download the Google Apps, go into Google Play Store settings and turn off automatic updates.