Personally, I really think it should be up to the mod creator themselves whether they should release their mod source or not and what kind of benefits the community gets from it. Like, for example, if it's something the community can learn from (simple mfk scripts, vehicle ports), then those mods should best be decompilable. However, for things like main mods I really don't think it's necessary, especially since one of the reasons the .lmlm format was created was to compress large mod file sizes anyways.
Besides, how many users join this board on a regular basis? Making mods like DM open source will probably have hundreds stealing its content and flooding the forums with what they call their "original" mods.