Personally I think they don't mind since its extending the life of the game. I know quite a few players who would have given up on this game a long time ago if it wasn't for mods. Me included.
Exactly this. If it wasn't for the modmaker, I would probably return to the game for a day or two at most. But I've been playing for 2 months now fresh again since I started using the mod tool with adding new challenges to the me3mp. Aside from giving you ability to make your own balance changes to the game, the best part of it is probably the custom wave editor. This alone can really change the pace and feel of the game. I made some very terrifying, challenging and fun enemy compositions with revamped enemy stats and abilities that will both scare and challenge you, because the old game was getting stale and it remained stale since they stopped making changes to it. I also made most the player kits and weapons better to widen the viability of different loadouts for platinum, diamond and harder custom difficulties and it has become pretty much a new game; me3mp 2.0 for me.
Since I do not support cheating nor I have any need for, my games are much harder to fight trough and actually take longer so it's not an effective way to farm, but it's all for the sake of making it more interesting. Highly recommend to try the modmaker, or just send me a message to join a custom game of mine, you are very much welcome to do so.
Mgamerz, you should also add me and try to play some of my custom wave setups sometime.. I didn't try the older mods on the site and original diamond difficulty but whenever I tried forking it I didn't see any changes trough the website so I'm actually kind of wondering if it's tweaked as heavily as mine.