I haven't tried, though it should be very easy. Generally the DTRules runtime requires about 100 MB to run (more or less, depending upon the size of your decision tables) and most Android phones have at least 10x that. The jars are pretty small as well.
Since the Rules Engine uses no external jars, just executing decision tables should be very easy. Most likely you will want to pack everything into the jar rather than use the file system. DTRules will attempt to open resources as well as files when loading rule sets.
If you are willing to give it a try, I would love to hear how it works out. If you run into any problems, then I would be happy to work with you to resolve them!
Good luck!
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Paul Snow
skype: paulsnx2