Sorry for necroposting but I've rediscovered
this and was pleasantly surprised by how active the developers have been, and how some of the filter's variations are available ready-to-use as shaders or as a standalone C code, etc. (see the UPDATES at the end of the page). They offer several levels of correction, depending on how much each variation fits with the style of a game.
If the license thing is not an issue, as it seems to be suggested above, then I'm still pushing in favor of adding the
xBR algorithm. It could even allow to drop the other algorithms altogether (except nearest neighbour), which means less maintenance.