Hello Nicci, I noticed your posting, and am not responding to answer your question, because I have no idea of how to resolve that issue. Here just outside of Savannah Ga. where I live we have the opposite situation, our moss is brown and dead looking in the winter and lush and green during the spring and summer. My question of you is if you might consider trading mosses. I am establishing a wildlife refuge on some property that I recently purchased and the rear is being done to resemble a redwood forest with ferns and mosses, and would love to have some mosses that would stay green during the winter month. If you would check out my trade page I may have other items as well to tempt you and if not thats ok. Thank you for your consideration. Chaz

Softening of mosses and growing mosses out of their natural range.
Keeping moss green in the summer where it normally would go dry or dormant is probably possible by a misting regime done on a daily basis. Watering per se would not be necessary but at least a couple of light mistings to help cool down the moss and to provide some moisture might help. However everything is dependent upon the species of moss. Some mosses that do well in wet areas should be ok under this type of change wheareas mosses that are adapted to a dry period may not fare as well but this is also species dependent. You should experiment with a patch of the moss to see what happens.

Developing a redwood forest for Georgia sounds interesting and I hope that all considerations for temperature and moisture needs have been considered. Since your forest has not been created i would recommend first of all getting the trees to grow successfully before developing an understory. I believe that your major challenge is the soil characteristics of your area and dealing with heat.
Since you did not mention which Redwood you are using (Sempervirens or Sequoiadendron) the type of understory will vary. I do believe that there are Georgia mosses that will remain green in the summer. Check out those found near streams or wet areas and in the cooler and shadier woods of your region.

Had a thought that I think is relevant for Chaz.
Developing a wildlife refuge. Why a redwood forest? What is there already? What kind of wildlife are you interested in providing sanctuary for? It would seem to me that you would make use of the natural resources of the area to encourage those native critters to seek solace there. This would be more successful if they were provided the kinds of plants that they depend on to survive and this would ten to preclude any alien implants such as redwoods. Georgia has a very diverse range of habitats to emulate but the most important element you must include is water, either moving or pooled. Then develop your refuge. I would forget the nonnative plants and stick to what grows naturally in the region.