Suggestions for setup of a terminal server to allow 5-20 users to access a virtual application on multiple devices.

I support a small group of about 15 users who access a terminal application like Accuterm. Installing the actual application on devices is problematic due to constant emulation problems. I want to share out the app on a server 2012 Gateway using RemoteApp so that they can access the application on their internal PC's and Macs and remotely on laptops, tablets and phones. Accessed in a virtual window, the application can be scaled without emulation problems. The problem is the per-user licensing cost. I've also looked at Parallels application server. Any suggestions on a solution without heavy licensing costs?

Thank you