Boost Software License
The permissive licence from the Boost C++ libraries that drops the requirement to ship licence text with compiled programs.
Boost had long let each library pick its own licence, and in 2003 the project settled on a common text. It differs from MIT in one small but significant way: the notice must accompany source code, but not machine code. A program that statically links half of Boost doesn't have to bundle anything. For a C++ library made largely of templates that end up compiled into the user's binary, that was the right trade-off.
Its SPDX identifier is BSL-1.0, which is endlessly confused with the Business Source License, left to make do with BUSL-1.1. One is open source; the other explicitly isn't. Acronyms are not the law's strong suit.