That's the difference. dmsguild is
not a magazine, it paid if you were hired to write something. Dmsguild license is give us your creation on spec to do whatever we want with & use however we want and you are forbidden from monetizing or sharing it in any other way regardless of if we do anything with it. Those terms are fine if you need to use dmsguild because your making an adventure for one of WotC's settings, but not so much if you are making rules or content like spells & equipment not tied to a specific setting. Even if you publish something on dmsguild, the license is so restrictive that just trying to get it published on a totally unrelated market with nothing to do with wotc like
this obscure nobody of a website is all but impossible unless your content is so popular wotc tells them to add it.