It can be done, however, no one will talk to you because the audio will sound like garbage and all it will do is piss people off. My suggestion is to buy a D-Star radio. Also, if you d not have a local repeater, consider a DVAP as well.
Can it be done? Sure, but I hope you're ready for a lot of problems. The first 'gripe' with EchoLink is that no one seems to understand how to adjust audio levels, it isn't simple if you don't know how/why you should. The second problem is that D-Star is proprietary, and a limited (expensive) resource. You would be using two internet connections instead of just one, and what's the point?
(Can you tell I'm not enthused with either of them? Oh well...)
This has been done before, and I would strongly recommend against letting analog speech into a digital network like D-STAR. If you do this, prepare to be removed from the trust server. I second everything W2GLD has said.
Also, D-STAR isn't proprietary, as it's open-source and created by JARL. The codec, however, is proprietary.