It's likely people who previously purchased/downloaded the app will still be able to access it in their purchased history. Often times pulled apps remain available for previous owners even if not accessible for new sales but I'm not sure on all the specifics.
Its always a shame if a fine game does not make any income. I hope he will decide against pulling it. What can we do to save the game? Anyways, I´ve just downloaded it, as I´m into Dungeon Crawlers.
I understand from many situations like this that the problem with iOS game development is that often times it's not profitable or rewarding as anything beyond a hobby. Especially for "indie" developers it's very cut throat. In part customers aren't willing to pay much for mobile apps. Also there's so much low quality scam shovelware on App Store sometimes it's hard to tell the quality games from lesser known developers out of the muck. Tumulus of Fen is a worthy title worth getting while you can, whatever the cause for it being overlooked is.
This is true, thats why good review sites are needed that also cover small indie titles. I gave "Tumulus Of Fen" a spin today and it really is a great crawler as far as I could tell. I´ve also written a small article about it being free on my blog and added Sanukus Gameplay Video to it. I know it´s a bit late though. Maybe the guy behind the game should hook up with a publisher (Chillingo, 10Tons etc.) to save the first part of the game and make it permanently free (as has been done with Undercroft), then develop a second title with better marketing via this new publisher. This way the first part could serve as advertising and us players would not lose the game. In my opinion too much work has been put into this for just letting it fade away.
Tumulus of Fern needs better control. If the developer is reading, please replace swiping with directional buttons in your sequel.
Another explanation is that most people want polished looking games. This game the screenshots arent going to attract anyone who doesnt really know what kind of game this is.