The 24-year-old has only made two appearances since joining the Millers in the summer and has spent time on loan at Bury.
He scored two goals in nine appearances for the Shakers before his spell was cut short after picking up a groin injury which required surgery.
But having returned to fitness and with no prospect of breaking into Steve Evans' team, he has headed to London.
Dons boss Neal Ardley told the club's official website: "Danny was a player who I was keen on in the summer and I sat down with him then, but we lost out because he wanted to play at a higher level.
"That has not worked out for him so far this season. We liked what we saw when we watched Danny last season and when he played against us for Bury.
"Danny fits the mould of player that we were aiming to bring in. He has good experience, he is hard-working and brings a lot of the attributes that we want from a centre-forward.
"He will be a big player for us during the rest of this season."
- Sports & Recreation