if i got your question the answer is "no", it will interoperate with other vendors.. it is true that Cisco very often writes down its solutions before the other companies can even understand what a solution can be (TDP is my favorite example) but definitely you should read this:
and the updated version
Although each vendor has its own way to implement a standard, there are some features that MUST be respected.
Hopt it helps
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Is Cisco IP multicast proprietary? Will it interoperate with other routers that use PIM-SM (sparse mode)?
In answer to your first question, depends what "flavor" of Cisco multicast we're discussing.
In answer to your second question, likely will if other vendor adheres to the RFCs that Alessio provided.
In addition to my esteemed friend's answers here, for all practical purposes, Cisco's implementation of PIM-SM and BSR is a standard one, meaning that any other router that also implements standard PIM-SM should be capable of seamless interoperation with Cisco's multicast implementation. Therefore, I do not believe you should be concerned about any basic interoperability issues. The Auto-RP is a proprietary mechanism but considering BSR, you should avoid Auto-RP anyway.