xtc/third_party

Pinned plugin ABI headers

No plugin binaries or SDK runtime library are bundled. Updates are explicit, reviewed source changes; ordinary builds never fetch from the network.

Headers	Upstream revision	License	Maintenance/build impact
clap/include	free-audio/clap, a47f6badb49d948fd009998f28309cdab78979c9	MIT, clap/LICENSE	Active CLAP header specification, pinned snapshot; C99 compile-time dependency only
vst3/vst3_c_api.h	steinbergmedia/vst3_c_api, 93a116f7c6c52a317ec3aaee9b13789068b5234e	BSD-3-Clause, vst3/LICENSE.txt	Official generated C ABI; review compatibility when updating the SDK snapshot; no C++ runtime adapter

Files are unmodified upstream snapshots. The VST3 header's opening comment refers to its accompanying license; that upstream license is retained verbatim. Install and binary packages include both notices under the xtc license directory. These headers define interoperability ABIs, not a grant to redistribute user plugins.

src/plugin/vst2_abi.h is original minimal Linux compatibility declarations; no Steinberg VST2 SDK, implementation or VST2-wrapping SDK is copied or distributed. Legacy VST2 support does not grant SDK/trademark/plugin distribution rights. There is no VST2 plugin-building target for third-party SDKs. The original test fixture implements only the ABI subset needed to test this host.

Optional full-SDK examples in examples/steinberg compile from explicitly supplied external VST3/ASIO SDK roots. Normal builds do not fetch or link them; no external SDK source or ASIO runtime is included in source/binary packages. See SDK integration and licenses.

The optional examples/juce integration uses an external JUCE source root, not vendored headers. The inspected JUCE 9.0.4 revision is AGPLv3/commercial; a commercial licence may be required. Original example source does not relicense JUCE or its dependencies. JUCE-linked outputs stay outside normal install and package targets. See JUCE dependency/license details.