Yes it was - and then we had the security breach. :(
After the forum upgrade from vb3 to vb4 last February we put Tapatalk on the shopping list for plugins and it was duly installed. It needed testing before being available for all but before we managed to get around to arranging that, the bad guys broke in and the forum software had to be completely re-installed from scratch. It looks as though the Tapatalk plugin was never re-installed and none of us noticed because we had been distracted by the fallout from the security breach. Sorry about that.
Off the top of my head and this is not Forum Council policy. We'd probably need to discuss this plugin again. If there is still a real appetite for using Tapatalk we'd have to ask Canonical sysadmins to re-install it and that is quite a (necessary) bureaucratic process. Every plugin has the potential to introduce a security hole and although it was approved earlier this year, this time around it I'm sure it would be looked at with a gimlet eye. So - comments from Ubuntu Forums Members please.
One last thought - a few weeks before the security breach someone complained that their tablet had told them that they could have the Tapatalk app for $4.99 when they visited the forum. Which just goes to prove the old adage about pleasing some of the people.