Can Counterparty work on blockchains other than bitcoin?

Short answer: Yes, if you’re willing to develop for it.

Long answer: The proof-of-burn concept of Counterparty, along with other features such as asset issuance, dividends, and betting are independent of the underlying currency, so long as the currency offers a way to implement either multi-sig transactions and/or OP_RETURN. Since most other currencies (or altcoins) are forks of Bitcoin, this allows implementation on other currencies to be relatively straightforward. For coins that implement additional features such as Peercoin and Namecoin, the integration process would require more work, but could still be done.

There are no current plans to implement Counterparty on other currencies as of now. Synchronizing Counterparty across different blockchains is difficult due to timing issues; therefore other implementations of Counterparty would most likely be on separate networks unless this issue can be worked out.