Not sure you are going to get a very definitive answer to something so specific, old and unsupported here.

I've not done it myself, but it might work.  If I were you, I'd contact Michael Klein at http://computerdirectionsinc.com/ and expect to pay him for his expertise in this area.

Nancy Duhon, Esq.
Duhon Technology Solutions, LLC
Master Certified Consultant for Sage Timeslips
Providing individual Consultations and Third Party Remote Desktop Support - including older/unsupported versions.
404-325-9779
[email protected]

This response is going to be generic in nature as opposed to a directed answer, but you should be able to get the answer you need from it.

For those unfamiliar with RemoteApp (now deprecated by Microsoft), it enabled a workstation to look as though it is launching an application from it's own local resources, when in reality the application was launched on a Remote Desktop Services/RDS server (a/k/a Terminal Server) and only that application is available to the end user.

When the icon is clicked, a connection to the RDS server is established and the program launched.  When the application is exited, the connection is immediately and all services terminated.

In the correct operation of Timeslips, the program is exited and various background tasks are accomplished as the program terminates.  In a RemoteApp shutdown, those clean up processes are not completed and bad things can, and often do, happen.  Licenses can get hung, the various tables that arbitrate who is currently logged in and using Timeslips are left in limbo and generally wreak havoc.  

Timeslips does not support this sort of configuration for these reasons.  

A conventional Client-Server connection, running the application on the workstation and hosting the database on the server is preferred.  A more traditional RDS connection to the server, with a proper closing of the application before exiting the RDS session will function properly as well.