Here you will find a list of apps that have been ported to the DR. There are two ways (current used) to install extra software for the DR, 1) only on the SD card, or 2) on the internal flash of the DR (with only a short-cut on the SD-card).
I am not aware that any of the ported problems caused any instabillity in the operating system. If this should happen however, you can re-install the lastest firmware, which will delete and rewrite the complete internal flash, so you would have a 'fresh' system again. This will also remove all programs that have been installed with method 2 explained above. (Only the short-cuts on the SD-card remain.)