First post, by MrFlibble
I've been coming across fan games based on commercial franchises from time to time, and there seems to be more than one that are in one way or another endorsed/allowed/supported by the original franchise's owners. However there seems to centralised source on such projects, and it seems that rather often this "semi-official" status is not advertised.
I'll list what I know so far:
o Black Mesa -- likely the most well known example. I don't know the details but this is endorsed by Valve.
o Transfusion -- Blood remake on the DarkPlaces engine. The Blood wiki states that the developers got a "quitclaim license" from Infogrames (then owners of the franchise) to use art assets from Blood and recreate the levels, monsters etc.
o Giana Worlds was an unofficial sequel to The Great Giana Sisters, based on an earlier unofficial DOS port of that game. Giana Sisters author Armin Gessert gave permission to release the Giana Worlds project, as outlined here.
o OpenGGS, an open source implementation of The Great Giana Sisters, uses the original art and music with permission from the authors. Or at least, it used to say so on the developer page which is now down.
o Giana's Return, yet another unofficial sequel to The Great Giana Sisters, was made with permission from original authors.
o WinSPWW2 is effectively a remake of Steel Panthers on the Steel Panthers II engine, with the code provided by SSI (on condition that the resulting game would not be used for profit).
o Steel Panthers: World at War is another Steel Panthers remake, this time using the Steel Panthers III code provided by SSI.
o Renegade-X, a remake of Command & Conquer: Renegade, is said to have received support and encouragement from Electronic Arts.
o AGD Interactive has produced a number of Sierra's Quest game remakes, which I think are with soome sort of official permission, but I can't find exact details right now.
o Chex Quest 3 finally got its official approval (and a remake).
o Street Fighter X Mega Man is a fan crossover of the two franchises that was endorsed by Capcom.
o Castlevania 2: The Lecarde Chronicles, a Castlevania fangame, was not suppressed by Konami on condition that it will not be used for profit.
o Twisted Insurrection is a Tiberian Sun mod/conversion (alternate universe sequel to Tiberian Dawn) featuring music by Frank Klepacki, which can be treated as a sign of semi-official endorsement, at least by (one of) the original developers of Command & Conquer.
o The Silver Lining was given a Fan License after community protested to copyright holders against a C&D order.
Any other examples you can name? If approval comes from original developer who is no longer the copyright owner, please specify these cases too.