Yeah, I don't actually know how the original is made/distributed. Could be free, could be paid... it doesn't really matter so far as infringement goes, though, unless the actual author has given permission or is using a permissive license of some sort. Free online often doesn't mean free
anywhere online, with whatever modifications whoever pleases to make. Can easily violate copyright law distributing or modifying a free work, heh, for all that the folks making them are usually too poor or too ideologically inclined towards sharing et al to really do anything about it.
... honestly, I usually don't really check with translated work, I just refrain from linking directly. If you assume it's infringement there's not going to be a problem even if it isn't

E: But yeah, web serials and LNs and whatnot tend to kinda' be the Dwarf Fortress of modern literature so far as metaphorical development cycles go, particularly if they get popular enough donations and/or ad funds can support the author fully or in part (and that's assuming they don't end up outright published and sold via normal distribution routes). Some end, some just keep going until the author dies or somethin'.