non-mls clubs can also pursue solidarity/training payments frompro clubs outside the US, but this actually isn't a change.
the change would be that now that MLS is supporting payments, presumably USSF will drop their public - and, more importantly, behind the scenes - opposition to non-mls clubs seeking payments.
one of the articles about this move said that MLS announcing at this time indicates that it's likely that the crossfire case for payments re: yedlin that's pending with FIFA's DRC committee will be resolved in favor of crossfire receiving payments. The previously announced due for the decision - late April this year - synchs with this.
re: non-mls clubs receiving payments from mls clubs for players is still unresolved. eg, when ER who moved form Albion to SD Surf and likely is heading to LAFC and then goes pro, there's nothing in place that says that LAFC (or other MLS club) has to pay Albion or SD Surf anything.
FIFA says that intra-country stuff like this is a matter for that country's federation rule making body.
A handful of the articles quoted the MLS VP that the MLS considering proposals for this.