There is circumstantial evidence, no direct evidence as contracts are not public. There is no evidence, (circumstantial or direct) that AMD is allowing partners to add DLSS.
Every single AMD sponsored game released since FSR2 launched does not include DLSS despite it being trivial to add if the work is being done for FSR2. For Unreal engine games it can be enabled by including a completely free plugin, the work is already done. Yet, the AMD sponsored games don't. There is even a game that announced DLSS support before it released and then removed it after becoming AMD sponsored (Boundary).