I'm sure they can be installed but also pretty sure you'll hit the resource limit in Free servers pretty quick. Recommend you upgrade to a premium package and use a donation box to pay for the server if you're not charging for use.
I used to run an older version TS server (long time ago... original TS2) and it was a memory hog. Maybe the source code for this one is compiled differently.
You can and if you got cPanel on your VPS check out cPGS as that has all the packages and low foot print versions ready for install all from WHM.
Might help alittle as well for easy setup, as i use it on my VPS and works a treat.