We hope to have support for a viable alternative to sctrans2 released by the end of the month. It's well underway in development, but won't be included in today's release as it's not quite ready yet.
Meantime (as has been discussed here on the forums before) sctrans2 does not "phone home" to verify its licensing keys at all, so they're not locked to a particular stream.
You wouldn't want to use the same MP3 license key on multiple streams as that would be a violation of your license agreement, but I suspect there are a lot of folks who won't be bothered and will do exactly that since there are no technical limitations preventing it -- the only things stopping them are legal ramifications of violating the licensing agreement (i.e.: it's piracy).
But if you had a spare, unused key that (for example) you bought to use on a different, former client's stream, you could always reuse it on a new stream, and I don't think that would violate your sctrans2 licensing agreement since you're only using it on one stream at any given time.