A negative for the ISC license: there has been controversy about "and/or" vs. "and" wording in the ISC license text. [1]

The OpenBSD project uses the "and" wording, whereas the license text on the OSI website uses the "and/or" wording.

Given all this, it seems to me that recommending the 2-clause BSD is the most straightforward option, because its only (and innocuous) issue is that it contains some no-longer-necessary language after the Berne convention agreements.

[1] From Wikipedia: When initially released, the license did not include the term "and/or", which was changed from "and" by ISC in 2007. Paul Vixie stated on the BIND mailing list that the ISC license started using the term "and/or" to avoid controversy similar to the events surrounding the University of Washington's refusal to allow distribution of the Pine email software.