Ryan C. Gordon, also known as icculus, has just updated his finger to answer to this news post in the AA forums. It looks like the Mac and Linux support for America's Army by icculus will stop in the future:

"I'm now paid for just the Linux server. The Mac and Linux clients were cancelled several versions ago." ... "The problem, though, is that I'm a busy, busy guy. There are paying clients that are waiting for me to give them my attention, and my TODO list is continuing to grow." ... "2.7 is coming soon, and I'm still fighting with the 2.6 clients. Future versions of the game will be adding more middleware that I can't keep up with and for which no one will be footing the bill." ... "2.6 might still make it out the door, 2.7 probably won't."