It should be viewed as acceptable to upload anyone's mods in their original state to any site, particularly if the original hosting has died.
1. Publicly releasing files (and for free) means the author intends them to be used.
2. Nobody (unless engaged in untoward behavior) directly receives compensation for their files. At best, one can receive ad- or other revenue from the hosting website (I expect some people here receive this). I expect this is the best argument one could make in opposition; however, this perhaps treads the edge of legality if one were to closely examine the TSL's EULA [particularly points 6 and 10] (we and Lucasarts all know TSLRCM is what built this website), and more importantly, contradicts the notion that mods are made by fans for enjoyment. If one desired $, that modder should find a career in the game industry.
3. If nobody receives compensation for publicly released files, then what modders are concerned with here is something else. There are some characters, unfortunately present within a segment of the population which I'll cheerfully term "nerds", who utilize their positions among certain small communities to inflate their egos. By appointing themselves the sole holder of what other humans seek, people who are generally unimportant in their everyday lives can achieve some measure of superiority through artificially restricting the supply of a sought-after commodity.
Now, some people might declare that is the prerogative of the modder to do, since he is the one who created the file. However, I (and others) think that freely distributing publicly created files is the essence of modding as a community, and therefore should be engaged in even over the objections of some capitalistic, corporate-minded people, whether external to the community or inside of it.