Heroes of Might and Magic III on iOS and Android.

As far as I know, VCMI is based on the WoG engine.

That's incorrect. VCMI supports WoG and other custom mods (forges and others), but their presence is not mandatory. The game runs on a clean SoD.
(Although WoG was required before)

But the VCMI creators also do not have the original "Heroes" texts: they use reverse engineering.

Well, they naturally don't have the original source code; no one does.
But in VCMI, they are rewriting the code from scratch. It's open source, and here it is:

http://sourceforge.net/p/vcmi/code/HEAD/tree/trunk/

Of course, the project is not yet fully completed, and there are still many unfinished parts.

The fact that some people offered to buy the "source code" of "Heroes" from the copyright holders, but received the answer: "there isn't any!" speaks in favor of the version that the "source code" of "Heroes" is hopelessly lost. And if they existed, it is unlikely that anyone would miss the opportunity to make some money by selling something that is lying around doing nothing anyway.

That's possible.

By the way

It already works on tablets.

This was on outdated versions; it's better not to remember them, as there will be many problems, crashes, freezes, and so on. The current version is 0.94, and you should start from it. But it hasn't been implemented yet.