Source Depot is very similar to Perforce since sd started as a p4 fork.

Incidentally, I remember one person at Microsoft who claimed to be involved in the decision to adopt sd circa 1999 saying that Microsoft has the right to turn sd into a product if it so chooses. (He/she was responding to contrary claims made on an internal email mailing list which was very widely read, so I assume if he/she was misremembering or lying he/she would have been called out.) Though ultimately MSFT made VSTS/TFS version control instead, which has striking resemblances in concepts to sd/p4.